@article{taniguchi_lindsey_2024, title={Acquisition of absorption and fluorescence spectral data using chatbots}, volume={12}, ISSN={["2635-098X"]}, url={https://doi.org/10.1039/D4DD00255E}, DOI={10.1039/D4DD00255E}, abstractNote={Spectra – the lifeblood of photochemistry – have been very difficult to find in the literature. Chatbots, remarkably, may enable their more efficient acquisition and prove to be generally powerful tools for searching the scientific literature.}, journal={DIGITAL DISCOVERY}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2024}, month={Dec} } @article{taniguchi_du_lindsey_2024, title={Appropriate handling of fluorescence spectra for accurate spectral overlap (J) values in Forster energy transfer (FRET) calculations}, volume={13083}, ISBN={["978-1-5106-7489-9"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.3025086}, journal={SPIE FUTURE SENSING TECHNOLOGIES 2024}, author={Taniguchi, Masahiko and Du, Hai and Lindsey, Jonathan S.}, year={2024} } @article{taniguchi_lindsey_2024, title={Performance of chatbots in queries concerning fundamental concepts in photochemistry}, volume={11}, ISSN={["1751-1097"]}, url={https://doi.org/10.1111/php.14037}, DOI={10.1111/php.14037}, abstractNote={Abstract The advent of chatbots raises the possibility of a paradigm shift across society including the most technical of fields with regard to access to information, generation of knowledge, and dissemination of education and training. Photochemistry is a scientific endeavor with roots in chemistry and physics and branches that encompass diverse disciplines ranging from astronomy to zoology. Here, five chatbots have each been challenged with 13 photochemically relevant queries. The chatbots included ChatGPT 3.5, ChatGPT 4.0, Copilot, Gemini Advanced, and Meta AI. The queries encompassed fundamental concepts (e.g., “Why is the fluorescence spectrum typically the mirror image of the absorption spectrum?”), practical matters (e.g., “What is the inner filter effect and how to avoid it?”), philosophical matters (“Please create the most important photochemistry questions.”), and specific molecular features (e.g., “Why are azo dyes non‐fluorescent?”). The chatbots were moderately effective in answering queries concerning fundamental concepts in photochemistry but were glaringly deficient in specialized queries for dyes and fluorophores. In some instances, a correct response was embedded in verbose scientific nonsense whereas in others the entire response, while grammatically correct, was utterly meaningless. The unreliable accuracy makes present chatbots poorly suited for unaided educational purposes and highlights the importance of domain experts.}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2024}, month={Nov} } @article{aravindu_taniguchi_bocian_lindsey_2024, title={Synthesis of (oxo)chlorin dimers chelated with thallium(III)}, volume={28}, ISSN={["1099-1409"]}, url={https://doi.org/10.1142/S1088424624500548}, DOI={10.1142/S1088424624500548}, abstractNote={Two target dimers have been prepared for fundamental studies of hole/electron transfer. Metalation with thallium(III) enables clocking of the rate of hole/electron transfer between the two macrocycles. Each dimer contains a diphenylethyne linker joining two identical hydroporphyrins (chlorin or oxochlorin). The linker is substituted at the 4,4′-positions whereas each (oxo)chlorin is joined at the 10-position. Each (oxo)chlorin is equipped with a gem-dimethyl group at the 18-position to stabilize the hydroporphyrin chromophore toward adventitious dehydrogenation and a 3,5-di-tert-butyl group at the 5-position to achieve increased solubilization in organic media. The dimers parallel a prior set of diphenylethyne-linked (oxo)chlorin constructs containing zinc-free base, zinc-zinc, and copper-copper metalation states that have been examined in studies of electronic communication. The building block (oxo)chlorins for preparing the thallium-containing dimers have been prepared in quantities of 32–404 mg, a scale up to 14-fold larger than previously. Thallation of the free base (oxo)chlorin dimers was achieved with excess TlCl 3 ⋅4H 2 O in CH 2 Cl 2 /CH 3 OH (3–4:1) upon overnight reaction at room temperature. The long-wavelength (Q[Formula: see text] absorption band of (oxo)chlorins lies between that of the zinc(II) and free base counterparts. Absorption spectral comparisons are provided of the thallium(III) and free base (oxo)chlorin monomers and dimers.}, number={08}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, author={Aravindu, Kunche and Taniguchi, Masahiko and Bocian, David F. and Lindsey, Jonathan S.}, year={2024}, month={Aug}, pages={527–535} } @article{wang_taniguchi_bocian_lindsey_2024, title={Synthesis of porphyrin triads chelated with thallium(III) for studies of ground-state hole/electron transfer}, volume={28}, ISSN={["1099-1409"]}, url={https://doi.org/10.1142/S1088424624500524}, DOI={10.1142/S1088424624500524}, abstractNote={Four target all-porphyrin triads have been prepared for fundamental studies of ground-state hole/electron transfer. Each triad contains thallium(III) porphyrins as bookends, which bear mesityl groups at the three non-linking meso-positions. The central porphyrin is a free base or thallium(III) porphyrin bearing mesityl or pentafluorophenyl groups at the two non-linking meso-positions. The linker is a 4,4 ′ -diphenylethyne unit joined at the porphyrin meso-positions. The net spacer between the two bookend thallium(III) porphyrins thus consists of diphenylethyne–porphyrin–diphenylethyne and is designed as a superexchange element for through-bond hole/electron transfer. The energetics of the superexchange element are tunable given the nature of the substituents and metalation state of the central porphyrin. The synthesis entailed Sonogashira coupling of two building blocks, a free base bis(4-iodophenyl)porphyrin and a mono-ethynylporphinato thallium(III) chloride. Two benchmark porphyrins also were prepared. Absorption spectral comparisons are provided including of the all-thallium(III) monomer, dimer, and triad.}, number={08}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, author={Wang, Jieqi and Taniguchi, Masahiko and Bocian, David F. and Lindsey, Jonathan S.}, year={2024}, month={Aug}, pages={515–526} } @article{taniguchi_lindsey_2023, title={Absorption and fluorescence spectra of open-chain tetrapyrrole pigments-bilirubins, biliverdins, phycobilins, and synthetic analogues}, volume={55}, ISSN={["1873-2739"]}, DOI={10.1016/j.jphotochemrev.2023.100585}, abstractNote={Open-chain tetrapyrroles are ubiquitous and abundant in living organisms (algae, animals, bacteria, and plants), including examples such as bilirubin, biliverdin, phycocyanobilin, phycoerythrobilin, and urobilin. The open-chain tetrapyrroles, collectively termed bilins, arise from biosynthesis or degradation of tetrapyrrole macrocycles. Bilins are now known to play a wide variety of biological roles encompassing light-harvesting (in phycobiliproteins), photomorphogenesis, signaling, and redox chemistry. The absorption spectra of bilins spans the ultraviolet (UV), visible, to near-infrared (NIR) regions depending on the degree of conjugation, thereby providing a wide range of colors from red/orange to blue/green. The fluorescence intensity of bilins is often quite low and hence fewer spectra are available, but can be increased substantially by structural rigidification, as evidenced by the wide use of biliproteins as fluorescent labels. The present article describes a database of absorption and fluorescence spectra of bilins from natural and synthetic origins for 220 compounds (270 absorption and 13 fluorescence spectral traces). Spectral traces of bilins published over the past ∼50 years have been digitized and assembled along with information concerning solvent, photochemical properties (molar absorption coefficient and fluorescence quantum yield), and literature references. The spectral traces (xy-coordinate data files) can be viewed, downloaded, and accessed at www.photochemcad.com. The accessibility of spectral traces in digital format should facilitate identification and quantitative calculations of interest in diverse scientific areas.}, journal={JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2023}, month={Jun} } @article{tran_wang_matsumoto_liu_jing_nalaoh_nguyen_taniguchi_lindsey_2023, title={Bacteriochlorin syntheses - Status, problems, and exploration}, volume={8}, ISSN={["1099-1409"]}, url={https://doi.org/10.1142/S1088424623501171}, DOI={10.1142/S1088424623501171}, abstractNote={ Bacteriochlorins – Nature’s near-infrared (NIR) chromophores – are distinguished by an intense ([Formula: see text] ∼;105 M[Formula: see text]cm[Formula: see text] long-wavelength absorption band in the ∼;700–1000 nm. The development of routes to prepare synthetic, tailorable bacteriochlorins holds promise for multiple disciplines where NIR-light-promoted photoactivity is of interest. A de novo route to bacteriochlorins equipped with a stabilizing gem-dimethyl group in each pyrroline ring was discovered in 2003. Continued development in this arena over 20 years has led to additional routes as well as methods to install substituents at selected positions about the perimeter of the macrocycle. The present paper reports studies that highlight substantial limitations of existing synthetic routes, including stymied access to multi-bacteriochlorin arrays and the inability to install (in a rational way) distinct groups at opposite sides of the macrocycle. The origins of the limitations are traced to particular stages of the chemistry ranging from derivatizing pyrroles, creating pyrrolines, constructing and elaborating dihydrodipyrrins, coupling dihydrodipyrrins, and forming macrocycles. Through exploration of a dozen aspects of bacteriochlorin syntheses, 60 new compounds (and nine known compounds via improved syntheses) have been prepared and characterized; the data include 20 single-crystal X-ray diffraction analyses. The research taken together points to areas of focus to fulfill the promise of this fascinating class of compounds. }, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, author={Tran, Vy-Phuong and Wang, Pengzhi and Matsumoto, Nobuyuki and Liu, Sijia and Jing, Haoyu and Nalaoh, Phattananawee and Nguyen, Khiem Chau and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2023}, month={Aug} } @misc{taniguchi_larocca_bernat_lindsey_2023, title={Digital Database of Absorption Spectra of Diverse Flavonoids Enables Structural Comparisons and Quantitative Evaluations}, volume={86}, ISSN={["1520-6025"]}, url={https://doi.org/10.1021/acs.jnatprod.2c00720}, DOI={10.1021/acs.jnatprod.2c00720}, abstractNote={Flavonoids play diverse roles in plants, comprise a non-negligible fraction of net primary photosynthetic production, and impart beneficial effects in human health from a plant-based diet. Absorption spectroscopy is an essential tool for quantitation of flavonoids isolated from complex plant extracts. The absorption spectra of flavonoids typically consist of two major bands, band I (300-380 nm) and band II (240-295 nm), where the former engenders a yellow color; in some flavonoids the absorption tails to 400-450 nm. The absorption spectra of 177 flavonoids and analogues of natural or synthetic origin have been assembled, including molar absorption coefficients (109 from the literature, 68 measured here). The spectral data are in digital form and can be viewed and accessed at http://www.photochemcad.com. The database enables comparison of the absorption spectral features of 12 distinct types of flavonoids including flavan-3-ols (e.g., catechin, epigallocatechin), flavanones (e.g., hesperidin, naringin), 3-hydroxyflavanones (e.g., taxifolin, silybin), isoflavones (e.g., daidzein, genistein), flavones (e.g., diosmin, luteolin), and flavonols (e.g., fisetin, myricetin). The structural features that give rise to shifts in wavelength and intensity are delineated. The availability of digital absorption spectra for diverse flavonoids facilitates analysis and quantitation of these valuable plant secondary metabolites. Four examples are provided of calculations─multicomponent analysis, solar ultraviolet photoprotection, sun protection factor (SPF), and Förster resonance energy transfer (FRET)─for which the spectra and accompanying molar absorption coefficients are sine qua non.}, number={4}, journal={JOURNAL OF NATURAL PRODUCTS}, author={Taniguchi, Masahiko and LaRocca, Connor A. and Bernat, Jake D. and Lindsey, Jonathan S.}, year={2023}, month={Apr}, pages={1087–1119} } @article{taniguchi_wu_sterling_lindsey_raghavachari_berezin_2023, title={Digitization of print-based absorption and fluorescence spectra extracting clarity from clutter}, volume={12398}, ISBN={["978-1-5106-5901-8"]}, ISSN={["1605-7422"]}, DOI={10.1117/12.2651694}, abstractNote={Absorption and fluorescence spectra are central to the photosciences. The PhotochemCAD initiative, aimed at assembling digital databases of absorption and fluorescence spectra for use across the photosciences, now comprises <1000 absorption spectra and <500 fluorescence spectra for ~1000 compounds along with companion photophysical parameters (molar absorption coefficient, fluorescence quantum yield) and citations to the originating scientific literature. The spectral databases have chiefly been assembled by digitizing spectra from the vast print literature. The conversion of print spectra to digital form presents several technical challenges: (1) print spectra are plagued by line crossing from overlaid spectra, use of discontinuous lines, and interference from grids, tick marks, and the graph baseline; (2) the print spectrum in some cases lacks wavelength markers or is annotated with markers at odds with values in the accompanying text; and (3) the digitized spectra often are composed of data with uneven wavelength (x-axis) intervals. Here, manually assisted digitization – wherein the user steps through a print spectrum with hand-eye assistance to create the corresponding digital dataset – is compared with automated digitization. Graphical features that bear on use of each method are outlined. Two spreadsheet-based tools have been developed for application following digitization: (i) conversion of xy-coordinate data from uneven to uniform x-axis intervals, and (ii) calibration of the digitized spectrum with appropriate wavelength values. The two tools enable more accurate rendition of print spectra into digital form, as required for qualitative comparisons and quantitative calculations, and have been added to the PhotochemCAD website (http://www.photochemcad.com).}, journal={REPORTERS, MARKERS, DYES, NANOPARTICLES, AND MOLECULAR PROBES FOR BIOMEDICAL APPLICATIONS XIV}, author={Taniguchi, Masahiko and Wu, Zhiyuan and Sterling, Caitlin and Lindsey, Jonathan S. and Raghavachari, Ramesh and Berezin, Mikhail Y.}, year={2023} } @article{nguyen_tran_wang_zhang_wu_taniguchi_lindsey_2023, title={Four Routes to 3-(3-Methoxy-1,3-dioxopropyl)pyrrole, a Core Motif of Rings C and E in Photosynthetic Tetrapyrroles}, volume={28}, ISSN={["1420-3049"]}, url={https://doi.org/10.3390/molecules28031323}, DOI={10.3390/molecules28031323}, abstractNote={The photosynthetic tetrapyrroles share a common structural feature comprised of a β-ketoester motif embedded in an exocyclic ring (ring E). As part of a total synthesis program aimed at preparing native structures and analogues, 3-(3-methoxy-1,3-dioxopropyl)pyrrole was sought. The pyrrole is a precursor to analogues of ring C and the external framework of ring E. Four routes were developed. Routes 1–3 entail a Pd-mediated coupling process of a 3-iodopyrrole with potassium methyl malonate, whereas route 4 relies on electrophilic substitution of TIPS-pyrrole with methyl malonyl chloride. Together, the four routes afford considerable latitude. A long-term objective is to gain the capacity to create chlorophylls and bacteriochlorophylls and analogues thereof by facile de novo means for diverse studies across the photosynthetic sciences.}, number={3}, journal={MOLECULES}, author={Nguyen, Khiem Chau and Tran, Anh Thu Nguyen and Wang, Pengzhi and Zhang, Shaofei and Wu, Zhiyuan and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2023}, month={Feb} } @article{liu_taniguchi_goel_lindsey_2024, title={Rapid screening of dyes for self-aggregation, adsorption and metabolic integrity - Quantitative metrics as a prelude to biological studies}, volume={223}, ISSN={["1873-3743"]}, url={https://doi.org/10.1016/j.dyepig.2023.111914}, DOI={10.1016/j.dyepig.2023.111914}, abstractNote={The development of dyes for biological applications typically begins with synthesis, is followed by spectroscopic/photophysical characterization, and culminates in testing with cultured cells or in animals. The present work describes a set of facile, low-technology, in vitro, largely quantitative absorption spectrophotometric assays in aqueous solution as a prelude to biological studies. The assays include the following: (1) Self-aggregation in phosphate-buffered saline (PBS), with or without the presence of 3 % bovine serum albumin (BSA), via reciprocal change in concentration and pathlength; (2) Adsorption to solid materials as biomolecular surrogates, including cellulose, chitosan, polyethylene (PE), styrene-divinylbenzene beads (XAD-4), polyacrylic beads (XAD-7), anion exchange beads (IRA-67), cation exchange beads (CG-50), polytetrafluoroethylene (PTFE) membranes, and Nylon membranes; (3) Hydrophilicity/hydrophobicity assessment, by measurement (not calculation) of logP values; and (4) Metabolic integrity, by exposure to a rat liver homogenate. Twenty-two dyes were examined in the assays. The dyes represent diverse classes (acridine, anthraquinone, azo, benzimidazole, coumarin, cyanine, flavonoid, naphthalene, phthalocyanine, polyene, tetrapyrrole, triarylmethine, xanthene), polarity (anionic, cationic, nonionic, hydrophobic, amphipathic), and absorption (ultraviolet, visible, near-infrared). As one example, indocyanine green (ICG), an FDA-approved dye for in vivo use, (i) aggregates at the concentration of 5 μM but disaggregates in the presence of BSA; (ii) in PBS is very adsorptive (>80 % binding) to various materials (cellulose, chitosan, PE, IRA-67, CG-50, PTFE, Nylon) and quite adsorptive (50–80 % binding) to XAD-4 and XAD-7, (iii) exhibits only marginal preference for water versus 1-octanol (1.5:1), and (iv) is largely digested by rat liver homogenate. A single dye can be examined in the span of one day. The quantitative metrics should prove valuable for establishing biologically relevant features of diverse dyes by simple studies in aqueous solution.}, journal={DYES AND PIGMENTS}, author={Liu, Qihui and Taniguchi, Masahiko and Goel, Shreya and Lindsey, Jonathan S.}, year={2024}, month={Apr} } @misc{nguyen_zhang_liu_zhang_jin_taniguchi_miller_lindsey_2023, title={Tolyporphins-Exotic Tetrapyrrole Pigments in a Cyanobacterium-A Review}, volume={28}, ISSN={["1420-3049"]}, url={https://doi.org/10.3390/molecules28166132}, DOI={10.3390/molecules28166132}, abstractNote={Tolyporphins were discovered some 30 years ago as part of a global search for antineoplastic compounds from cyanobacteria. To date, the culture HT-58-2, comprised of a cyanobacterium–microbial consortium, is the sole known producer of tolyporphins. Eighteen tolyporphins are now known—each is a free base tetrapyrrole macrocycle with a dioxobacteriochlorin (14), oxochlorin (3), or porphyrin (1) chromophore. Each compound displays two, three, or four open β-pyrrole positions and two, one, or zero appended C-glycoside (or –OH or –OAc) groups, respectively; the appended groups form part of a geminal disubstitution motif flanking the oxo moiety in the pyrroline ring. The distinct structures and repertoire of tolyporphins stand alone in the large pigments-of-life family. Efforts to understand the cyanobacterial origin, biosynthetic pathways, structural diversity, physiological roles, and potential pharmacological properties of tolyporphins have attracted a broad spectrum of researchers from diverse scientific areas. The identification of putative biosynthetic gene clusters in the HT-58-2 cyanobacterial genome and accompanying studies suggest a new biosynthetic paradigm in the tetrapyrrole arena. The present review provides a comprehensive treatment of the rich science concerning tolyporphins.}, number={16}, journal={MOLECULES}, author={Nguyen, Kathy-Uyen and Zhang, Yunlong and Liu, Qihui and Zhang, Ran and Jin, Xiaohe and Taniguchi, Masahiko and Miller, Eric S. and Lindsey, Jonathan S.}, year={2023}, month={Aug} } @article{roy_magdaong_jing_rong_diers_kang_niedzwiedzki_taniguchi_kirmaier_lindsey_et al._2022, title={Balancing Panchromatic Absorption and Multistep Charge Separation in a Compact Molecular Architecture br}, volume={12}, ISSN={["1520-5215"]}, url={https://doi.org/10.1021/acs.jpca.2c06040}, DOI={10.1021/acs.jpca.2c06040}, abstractNote={A panchromatic triad and a charge-separation unit are joined in a crossbar architecture to capture solar energy. The panchromatic-absorber triad (T) is comprised of a central free-base porphyrin that is strongly coupled via direct ethyne linkages to two perylene-monoimide (PMI) groups. The charge-separation unit incorporates a free-base or zinc chlorin (C or ZnC) as a hole acceptor (or electron donor) and a perylene-diimide (PDI) as an electron acceptor, both attached to the porphyrin via diphenylethyne linkers. The free-base porphyrin is common to both light-harvesting and charge-separation motifs. The chlorin and PDI also function as ancillary light absorbers, complementing direct excitation of the panchromatic triad to produce the discrete lowest excited state of the array (T*). Attainment of full charge separation across the pentad entails two steps: (1) an initial excited-state hole/electron-transfer process to oxidize the chlorin (and reduce the panchromatic triad) or reduce the PDI (and oxidize the panchromatic triad); and (2) subsequent ground-state electron/hole migration to produce oxidized chlorin and reduced PDI. Full charge separation for pentad ZnC-T-PDI to generate ZnC+-T-PDI- occurs with a quantum yield of ∼30% and mean lifetime ∼1 μs in dimethyl sulfoxide. For C-T-PDI, initial charge separation is followed by rapid charge recombination. The molecular designs and studies reported here reveal the challenges of balancing the demands for charge separation (linker length and composition, excited-state energies, redox potentials, and medium polarity) with the constraints for panchromatic absorption (strong electronic coupling of the porphyrin and two PMI units) for integrated function in solar-energy conversion.}, number={50}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Roy, Arpita and Magdaong, Nikki Cecil M. and Jing, Haoyu and Rong, Jie and Diers, James R. and Kang, Hyun Suk and Niedzwiedzki, Dariusz M. and Taniguchi, Masahiko and Kirmaier, Christine and Lindsey, Jonathan S. and et al.}, year={2022}, month={Dec} } @article{taniguchi_bocian_holten_lindsey_2022, title={Beyond green with synthetic chlorophylls - Connecting structural features with spectral properties}, volume={52}, ISSN={["1873-2739"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85131670645&partnerID=MN8TOARS}, DOI={10.1016/j.jphotochemrev.2022.100513}, abstractNote={The distinct features of chlorophylls in photosynthesis have led to the formation of numerous derivatives for applications encompassing solar energy conversion, molecular photonics, photodynamic therapy, and molecular imaging. Synthetic chlorins created de novo and bearing a geminal dimethyl group in the reduced ring have proved invaluable for fundamental studies. Four decades of research have led to accumulation of tabulated spectra for > 400 such synthetic chlorins with distinct structural frameworks (17-oxochlorins, 131-oxophorbines, chlorinimides) and substituents (alkyl, aryl, ethynyl, phenylethynyl, acetyl, formyl) located at specific (meso, β) positions. In this review, spectral traces (324 absorption, 247 fluorescence) are assembled along with photophysical data including the molar absorption coefficient (ε), fluorescence quantum yield (Φf) and singlet excited-state lifetime (τs). The review uses the accumulated spectral data derived from chlorins all containing a uniform molecular scaffold to (1) highlight the effects of molecular structure on spectral features, and (2) identify trends including how ε, Φf and τs vary with wavelength and other features. Use of a common geminal-dimethyl-substituted chlorin scaffold – beginning with no substituents, to one substituent at designated sites, and to 2 or more substituents – provides a systematic Aufbau approach for understanding the absorption spectra of chlorins on a path to and beyond the native chlorophylls. The review provides insights concerning the rational design of potent analogues of Nature’s preeminent red-region absorbers for potential utilization in diverse applications and is aimed at multiple audiences: those interested in spectral properties, tetrapyrrole photophysics, and the molecular design of new chromophores.}, journal={JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS}, author={Taniguchi, Masahiko and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2022}, month={Sep} } @article{taniguchi_taniguchi_zhang_goto_lindsey_2022, title={Chasing the green echiuran worm Bonellia in tidal pools of Okinawa}, volume={11979}, ISBN={["978-1-5106-4829-6"]}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85131381961&partnerID=MN8TOARS}, DOI={10.1117/12.2608722}, abstractNote={Bonellia viridis, a green marine echiuran worm known since the early 19th century in the Mediterranean Sea, typically lives in sediments or rock crevices at a depth underwater of 3–10 m, causing acquisition of samples to generally require diving. The size of the main body trunk of the female is about 8 cm, whereas the (dwarf) male is 1 to 3 mm long and lives inside the female. The green pigmentation of B. viridis stems from bonellin, a tetrapyrrole macrocycle containing a chlorin chromophore. Bonellin is believed to exert diverse physiological functions (masculinization and sex determination, chemical defense, cytotoxicity, and antimicrobial activity) but not photosynthesis as for the better known native chlorin, chlorophyll. The existence of bonellin poses physiological, biosynthetic, and evolutionary questions. Here, we report in-depth assessment of information concerning tides at a wide shallow beach in Okinawa, identifying narrowly restricted periods when acquisition of Bonellia specimens could be pursued without diving. Indeed, <15 specimens of B. sp. were collected from Odo beach, Itoman city, Okinawa prefecture, Japan [26°09' N, 127°71' E], at midnight on days when the tides were exceptionally low: March 6–12, 2016; December 22–27, 2018; and January 18–25, 2019. The specimens were acquired manually from small tidal pools upon walking near the outer reef flat (~300 m from the shore) during the extremely low tides. Reasonably facile access without diving to Bonellia in a region distant from the Mediterranean should expand study of the diversity of these unusual green worms.}, journal={FRONTIERS IN BIOLOGICAL DETECTION: FROM NANOSENSORS TO SYSTEMS XIV}, author={Taniguchi, Masahiko and Taniguchi, Minami and Zhang, Ran and Goto, Ryutaro and Lindsey, Jonathan S.}, year={2022} } @article{liu_rong_wu_taniguchi_bocian_holten_lindsey_2022, title={Panchromatic Absorbers Tethered for Bioconjugation or Surface Attachment}, volume={27}, ISSN={["1420-3049"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85139868890&partnerID=MN8TOARS}, DOI={10.3390/molecules27196501}, abstractNote={The syntheses of two triads are reported. Each triad is composed of two perylene-monoimides linked to a porphyrin via an ethyne unit, which bridges the perylene 9-position and a porphyrin 5- or 15-position. Each triad also contains a single tether composed of an alkynoic acid or an isophthalate unit. Each triad provides panchromatic absorption (350–700 nm) with fluorescence emission in the near-infrared region (733 or 743 nm; fluorescence quantum yield ~0.2). The syntheses rely on the preparation of trans-AB-porphyrins bearing one site for tether attachment (A), an aryl group (B), and two open meso-positions. The AB-porphyrins were prepared by the condensation of a 1,9-diformyldipyrromethane and a dipyrromethane. The installation of the two perylene-monoimide groups was achieved upon the 5,15-dibromination of the porphyrin and the subsequent copper-free Sonogashira coupling, which was accomplished before or after the attachment of the tether. The syntheses provide relatively straightforward access to a panchromatic absorber for use in bioconjugation or surface-attachment processes.}, number={19}, journal={MOLECULES}, author={Liu, Rui and Rong, Jie and Wu, Zhiyuan and Taniguchi, Masahiko and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2022}, month={Oct} } @misc{jing_rong_taniguchi_lindsey_2022, title={Phenylene-linked tetrapyrrole arrays containing free base and diverse metal chelate forms - Versatile synthetic architectures for catalysis and artificial photosynthesis}, volume={456}, ISSN={["1873-3840"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85122467651&partnerID=MN8TOARS}, DOI={10.1016/j.ccr.2021.214278}, abstractNote={Tetrapyrrole macrocycles are central to photosynthesis yet a single macrocycle does not carry out photosynthesis; rather, assemblies of tetrapyrrole macrocycles work in concert in antenna complexes, reaction centers, and electron-transport chains to harvest sunlight, funnel excited-state energy and separate charge for biological use. A longstanding theme in artificial photosynthesis has been to construct covalently linked “arrays” of metalated and free base tetrapyrrole macrocycles for fundamental studies of such processes, which entail excited-state and ground-state interactions. Among linkers in arrays chemistry, the 1,2-, 1,3-, or 1,4-disubstituted phenylene unit has proved very attractive owing to the resulting short distance, defined architecture, and appropriate extent of electronic coupling of adjacent macrocycles to give rapid electron and/or energy transfer while largely retaining desired spectral features. Eight distinct strategies to construct phenylene-linked tetrapyrrole arrays are identified in a review with comprehensive coverage since inception in the early 1970s through mid-year 2021. The arrays predominantly incorporate porphyrins with very few chlorins and bacteriochlorins, reflecting historic availability of synthetic methods for macrocycle formation. Of the eight strategies, only two appear applicable to (bacterio)chlorins. While studies in artificial photosynthesis have largely fueled this field, applications in catalysis have also been examined. Altogether >400 arrays are covered. The review delves into synthesis and molecular design, sketches photophysical properties, and suggests unrealized opportunities in arrays chemistry.}, journal={COORDINATION CHEMISTRY REVIEWS}, author={Jing, Haoyu and Rong, Jie and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2022}, month={Apr} } @article{karg_taniguchi_lindsey_moser_2022, title={Phyllobilins - Bioactive Natural Products Derived from Chlorophyll - Plant Origins, Structures, Absorption Spectra, and Biomedical Properties}, volume={12}, ISSN={["1439-0221"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85140841360&partnerID=MN8TOARS}, DOI={10.1055/a-1955-4624}, abstractNote={AbstractPhyllobilins are open-chain products of the biological degradation of chlorophyll a in higher plants. Recent studies reveal that phyllobilins exert anti-oxidative and anti-inflammatory properties, as well as activities against cancer cells, that contribute to the human health benefits of numerous plants. In general, phyllobilins have been overlooked in phytochemical analyses, and – more importantly – in the analyses of medicinal plant extracts. Nevertheless, over the past three decades, > 70 phyllobilins have been identified upon examination of more than 30 plant species. Eight distinct chromophoric classes of phyllobilins are known: phyllolumibilins (PluBs), phylloleucobilins (PleBs), phylloxanthobilins (PxBs), and phylloroseobilins (PrBs)–each in type-I or type-II groups. Here, we present a database of absorption and fluorescence spectra that has been compiled of 73 phyllobilins to facilitate identification in phytochemical analyses. The spectra are provided in digital form and can be viewed and downloaded at www.photochemcad.com. The present review describes the plant origin, molecular structure, and absorption and fluorescence features of the 73 phyllobilins, along with an overview of key medicinal properties. The review should provide an enabling tool for the community for the straightforward identification of phyllobilins in plant extracts, and the foundation for deeper understanding of these ubiquitous but underexamined plant-derived micronutrients for human health.}, journal={PLANTA MEDICA}, author={Karg, Cornelia A. and Taniguchi, Masahiko and Lindsey, Jonathan S. and Moser, Simone}, year={2022}, month={Dec} } @article{siwawannapong_nemeth_melander_rong_davis_taniguchi_carpenter_lindsey_melander_2022, title={Simple Dipyrrin Analogues of Prodigiosin for Use as Colistin Adjuvants}, volume={7}, ISSN={["1860-7187"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85133558458&partnerID=MN8TOARS}, DOI={10.1002/cmdc.202200286}, abstractNote={AbstractMultidrug resistant (MDR) bacteria are an increasing public health problem. One promising alternative to the development of new antibiotics is the use of antibiotic adjuvants, which would allow the continued use of FDA‐approved antibiotics that have been rendered ineffective due to resistance. Herein, we report a series of dipyrrins and pyrrole derivatives designed as analogues of prodigiosin and obatoclax, several of which potentiate the activity of colistin against Klebsiella pneumoniae, with lead compounds also potentiating colistin against Acinetobacter baumannii and Pseudomonas aeruginosa.}, number={16}, journal={CHEMMEDCHEM}, author={Siwawannapong, Kittipan and Nemeth, Ansley M. and Melander, Roberta J. and Rong, Jie and Davis, Jonathan R. and Taniguchi, Masahiko and Carpenter, Morgan E. and Lindsey, Jonathan S. and Melander, Christian}, year={2022}, month={Jul} } @article{diers_kirmaier_taniguchi_lindsey_bocian_holten_2021, title={A perspective on the redox properties of tetrapyrrole macrocycles}, volume={9}, ISSN={["1463-9084"]}, url={https://doi.org/10.1039/D1CP01943K}, DOI={10.1039/d1cp01943k}, abstractNote={Understanding the redox properties of tetrapyrroles requires deep insights into how structural/electronic alterations affect all four frontier molecular orbitals.}, number={35}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, publisher={Royal Society of Chemistry (RSC)}, author={Diers, James R. and Kirmaier, Christine and Taniguchi, Masahiko and Lindsey, Jonathan S. and Bocian, David F. and Holten, Dewey}, year={2021}, month={Sep} } @misc{taniguchi_lindsey_bocian_holten_2021, title={Comprehensive review of photophysical parameters (epsilon, Phi(f), tau(s)) of tetraphenylporphyrin (H2TPP) and zinc tetraphenylporphyrin (ZnTPP) - Critical benchmark molecules in photochemistry and photosynthesis}, volume={46}, ISBN={1873-2739}, url={https://doi.org/10.1016/j.jphotochemrev.2020.100401}, DOI={10.1016/j.jphotochemrev.2020.100401}, abstractNote={Tetraphenylporphyrin (H2TPP) and zinc tetraphenylporphyrin (ZnTPP) are widely used benchmark molecules in diverse photochemical studies given facile synthetic access, rich visible-region spectra, and broad structural analogy to chlorophylls. Yet the literature values for each key photophysical parameter – the molar absorption coefficient (ε), fluorescence quantum yield (Φf), and also singlet excited-state lifetime (τS) – vary over an astonishing range. Here, a comprehensive literature review (∼1940–September 2020) encompassing 871 publications is reported for these essential parameters. Each parameter is determined by measurement with distinct instrumentation and suffers idiosyncratic sources of error. The best values for H2TPP are ε = 460,000 cm−1·M−1, Φf = 0.090, and τS = 12.8 ns in Ar- purged toluene (Φf = 0.070, τS = 9.9 ns in toluene in air); the best values for ZnTPP are ε = 560,000 cm−1·M−1, Φf = 0.030, and τS = 2.1 ns in Ar-purged toluene (Φf = 0.029, τS = 2.0 ns in toluene in air). The choice of values for such parameters has far-reaching consequences in photochemistry ranging from fluorescence (or Förster) resonance energy transfer (FRET) processes to assessments of molecular brightness.}, journal={JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS}, publisher={Elsevier BV}, author={Taniguchi, Masahiko and Lindsey, Jonathan S. and Bocian, David F. and Holten, Dewey}, year={2021}, month={Mar}, pages={100401} } @article{rong_magdaong_taniguchi_diers_niedzwiedzki_kirmaier_lindsey_bocian_holten_2021, title={Electronic Structure and Excited-State Dynamics of Rylene-Tetrapyrrole Panchromatic Absorbers}, volume={125}, ISSN={["1520-5215"]}, url={https://doi.org/10.1021/acs.jpca.1c05771}, DOI={10.1021/acs.jpca.1c05771}, abstractNote={Panchromatic absorbers have potential applications in molecular-based energy-conversion schemes. A prior porphyrin-perylene dyad (P-PMI, where "MI" denotes monoimide) coupled via an ethyne linker exhibits panchromatic absorption (350-700 nm) and a tetrapyrrole-like lowest singlet excited state with a relatively long singlet excited-state lifetime (τS) and increased fluorescence quantum yield (Φf) versus the parent porphyrin. To explore the extension of panchromaticity to longer wavelengths, three arrays have been synthesized: a chlorin-terrylene dyad (C-TMI), a bacteriochlorin-terrylene dyad (B-TMI), and a perylene-porphyrin-terrylene triad (PMI-P-TMI), where the terrylene, a π-extended homologue of perylene, is attached via an ethyne linker. Characterization of the spectra (absorption and fluorescence), excited-state properties (lifetime, yields, and rate constants of decay pathways), and molecular-orbital characteristics reveals unexpected subtleties. The wavelength of the red-region absorption band increases in the order C-TMI (705 nm) < PMI-P-TMI (749 nm) < B-TMI (774 nm), yet each array exhibits diminished Φf and shortened τS values. The PMI-P-TMI triad in toluene exhibits Φf = 0.038 and τS = 139 ps versus the all-perylene triad (PMI-P-PMI) for which Φf = 0.26 and τS = 2000 ps. The results highlight design constraints for auxiliary pigments with tetrapyrroles to achieve panchromatic absorption with retention of viable excited-state properties.}, number={36}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, publisher={American Chemical Society (ACS)}, author={Rong, Jie and Magdaong, Nikki Cecil M. and Taniguchi, Masahiko and Diers, James R. and Niedzwiedzki, Dariusz M. and Kirmaier, Christine and Lindsey, Jonathan S. and Bocian, David F. and Holten, Dewey}, year={2021}, month={Sep}, pages={7900–7919} } @article{nguyen_zhang_taniguchi_lindsey_2021, title={Fluorescence Assay for Tolyporphins Amidst Abundant Chlorophyll in Crude Cyanobacterial Extracts}, volume={7}, ISSN={["1751-1097"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85110167749&partnerID=MN8TOARS}, DOI={10.1111/php.13474}, abstractNote={AbstractTolyporphins are distinctive tetrapyrrole natural products found singularly in a filamentous cyanobacterial‐microbial holobiont (termed HT‐58‐2) from Micronesia. The absorption and fluorescence features of tolyporphins resemble those of chlorophyll a, complicating direct analysis of culture samples. Treatment of the crude (unfractionated) organic extract (CH2Cl2/2‐propanol, 1:1) of HT‐58‐2 cultures with NaBH4 in methanol causes reduction of the peripheral ketone auxochromes, whereupon tolyporphins (predominantly 7,17‐dioxobacteriochlorins) exhibit a bathochromic shift (λabs ˜ 676 → ˜ 700 nm) and chlorophyll a (a 131‐oxochlorin) exhibits a hypsochromic shift (λabs 665 → 634 nm). Fluorescence excitation spectroscopy (at 368 and 491 nm with λem 710 nm) enabled detection of reduced tolyporphins amidst abundant reduced chlorophyll a (1:19 ratio), a detection sensitivity >5 times that without reduction. The resulting assay combines simple sample preparation from non‐axenic cultures at microscale quantities (2 mL, 2 μm), absence of any fractionation procedures, and fluorescence detection. Tolyporphins were readily detected in cultures of HT‐58‐2 at reasonable growth periods in the absence of environmental stressors, which was not possible previously.}, number={6}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, author={Nguyen, Kathy-Uyen and Zhang, Ran and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2021}, month={Jul} } @inproceedings{wu_kittinger_norcross_taniguchi_lindsey_2021, title={PhotochemCAD spectra viewer for web-based visualization of absorption and fluorescence spectra}, volume={11660}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85108458063&partnerID=MN8TOARS}, DOI={10.1117/12.2577840}, abstractNote={PhotochemCAD is a Microsoft Windows-based software program composed of spectral databases and program modules for diverse photochemical calculations and is aimed at addressing fundamental needs of the scientific community. Since initiation in the late 1980’s, ~1000 absorption/fluorescence spectra of ~500 organic compounds of interest across the wide photosciences field have been collected and are now available in PhotochemCAD 3. The spectra are accompanied by quantitative parameters (molar absorption coefficient, fluorescence quantum yield) where available and citations to the original source literature. Many web-based absorption/fluorescence spectra viewers are publicly accessible but are typically aimed at commercial sales by sponsoring companies. Here, a web-browser-based PhotochemCAD spectra viewer is described that enables overlay of spectra for comparative evaluation, can be used on any platform (Windows, Mac, Linux), and does not require downloading or installation of the program. The PhotochemCAD program, databases, and spectra viewer are accessible for free use at http://www.photochemcad.com.}, booktitle={Progress in Biomedical Optics and Imaging - Proceedings of SPIE}, author={Wu, Z. and Kittinger, A. and Norcross, A.E. and Taniguchi, M. and Lindsey, J.S.}, year={2021} } @article{lindsey_taniguchi_bocian_holten_2021, title={The fluorescence quantum yield parameter in Förster resonance energy transfer (FRET)—Meaning, misperception, and molecular design}, volume={2}, url={https://doi.org/10.1063/5.0041132}, DOI={10.1063/5.0041132}, abstractNote={The fluorescence quantum yield parameter in Förster resonance energy transfer (FRET) processes underpins vital phenomena ranging from light harvesting in photosynthesis to design of sensors for monitoring physiological processes. The criteria for choosing a donor for use in FRET processes include chemical features (solubility, bioconjugatability, synthetic accessibility, and stability) as well as photophysical properties pertaining to absorption (wavelength and molar absorption coefficient) and fluorescence (wavelength and fluorescence quantum yield). The value of the donor fluorescence quantum yield (Φf, or emphatically, Φf(D)) alone has sometimes been thought (erroneously) to place a ceiling on the possible quantum yield of energy transfer (Φtrans). A high value of the donor Φf, while attractive, is not at all essential; indeed, many valuable candidates for use as FRET donors have likely been excluded on the basis of this injudiciously applied filter. Such disregard is unwarranted. In this tutorial overview, the equations for FRET are reviewed along with pertinent core concepts in photophysics. An analogy using simple hydraulics provides a pedagogical tool for the non-aficionado to better understand photochemical kinetics. Ten examples are presented of donor–acceptor systems with donors that exhibit a range of Φf values (0.60, 0.59. 0.21, 0.17, 0.12, 0.118, 0.04, 0.018, 0.007, and 0.003; i.e., 60%–0.3%), yet for each corresponding donor–acceptor pair, the value of Φtrans is at least 0.70 and in some cases nearly 1.00 (i.e., 70%–100%). The systems encompass protein, synthetic inorganic, and synthetic organic architectures. The objectives of this illustrative review are to deepen understanding of FRET and to broaden molecular design considerations by enabling selection from among a far richer set of donors for use in FRET processes.}, number={1}, journal={Chemical Physics Reviews}, publisher={AIP Publishing}, author={Lindsey, Jonathan S. and Taniguchi, Masahiko and Bocian, David F. and Holten, Dewey}, year={2021}, month={Mar}, pages={011302} } @article{timothy j. o'donnell_gurr_dai_taniguchi_williams_lindsey_2021, title={Tolyporphins A-R, unusual tetrapyrrole macrocycles in a cyanobacterium from Micronesia, assessed quantitatively from the culture HT-58-2}, volume={6}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85109210079&partnerID=MN8TOARS}, DOI={10.1039/d1nj02108g}, abstractNote={Tolyporphins A–R are the newest additions to the family of native tetrapyrroles. LC-MS-dMRM and absorption spectroscopy have been employed for analysis of mixtures containing the 18 distinctive natural products.}, number={26}, journal={NEW JOURNAL OF CHEMISTRY}, author={Timothy J. O'Donnell and Gurr, Joshua R. and Dai, Jingqiu and Taniguchi, Masahiko and Williams, Philip G. and Lindsey, Jonathan S.}, year={2021}, month={Jun} } @article{taniguchi_lindsey_2021, title={Absorption and Fluorescence Spectral Database of Chlorophylls and Analogues}, volume={97}, ISSN={["1751-1097"]}, url={https://doi.org/10.1111/php.13319}, DOI={10.1111/php.13319}, abstractNote={AbstractAbsorption spectra and fluorescence spectra are essential for use across the photosciences, yet such spectra along with the all‐important values for molar absorption coefficient (ε) and fluorescence quantum yield (Φf) often are found with great difficulty. Here, a literature survey concerning the vital class of chlorophyll compounds has led to identification of spectra for 150 members. Spectra in print form have been digitized (with baseline corrections) and assembled into a database along with literature references, solvent identity and values for ε and Φf (where available). The database encompasses photosynthetic tetrapyrroles wherein the chromophore is a porphyrin (e.g. chlorophyll c1, protochlorophyll a), chlorin (e.g. chlorophyll a, bacteriochlorophyll c) or bacteriochlorin (e.g. bacteriochlorophyll a). Altogether, the database contains 305 absorption spectra (from 19 porphyrins, 109 chlorins and 22 bacteriochlorins) and 72 fluorescence spectra (from 10 porphyrins, 30 chlorins and 4 bacteriochlorins). The spectral database should facilitate comparisons and quantitative calculations. All spectra are available in print form in the Supporting Information. The entire database in digital form is available with the PhotochemCAD program for free downloading and further use at http://www.photochemcad.com.}, number={1}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, publisher={Wiley}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2021}, month={Jan}, pages={136–165} } @article{taniguchi_lindsey_2020, title={Absorption and fluorescence spectra of organic compounds from 40 sources - archives, repositories, databases, and literature search engines}, volume={11256}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85084177636&partnerID=MN8TOARS}, DOI={10.1117/12.2542859}, abstractNote={Absorption and fluorescence spectra are foundational data for studies in photochemistry as well as any area of science or technology that entails electronic spectroscopy. The data of interest include the spectra (graphs of intensity as a function of wavelength or wavenumber), the respective quantitative photophysical parameters – molar absorption coefficient [ε(λ)] and the fluorescence quantum yield [Φf] – and the conditions under which the data were obtained. Yet such qualitative and quantitative data are scattered across a wide landscape. Modern search engines provide access to much of the world’s published scientific literature (<108 articles) spanning <100 years but are surprisingly ineffective at pinpointing spectra and companion photophysical parameters. Manual curation has led to valuable collections albeit of uneven contents: some include spectra, others include only listings of spectral data (e.g., positions of peak intensity [λmax]), and many are not available in digital form. Numerous calculations in photophysics, such as propensity for Förster resonance energy transfer (FRET), require spectra and cannot be carried out with tabular listings of values of λmax, ε(λ) and Φf. Here, we summarize the spectral data available in 27 printed archives (beginning in the early 20th century), in repositories or databases at a dozen dedicated websites, and via scholarly literature search tools. The websites and search tools include PubChem, ChemSpider, NIST Chemistry WebBook, SciFinder, Reaxys, Google Scholar, Microsoft Academic, and Web of Science. This work is part of a long-term project to organize and assemble the world of spectral data for the molecular photosciences.}, journal={REPORTERS, MARKERS, DYES, NANOPARTICLES, AND MOLECULAR PROBES FOR BIOMEDICAL APPLICATIONS XII}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2020} } @article{cao_mehta_norcross_taniguchi_lindsey_2020, title={Analysis of Wikipedia pageviews to identify popular chemicals}, volume={11256}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85084186656&partnerID=MN8TOARS}, DOI={10.1117/12.2542835}, abstractNote={A new approach to assess popularity relies on analysis of the number of times a web article is viewed. Here, a strategy is described to identify chemicals of widespread interest. The strategy makes use of Wikipedia, a rapidly growing publicly editable web encyclopedia that has become an influential knowledge base. While the total number of chemicals mentioned in Wikipedia is unknown, use of the Wikipedia Chemical Structure Explorer (WCSE) developed by Novartis enables identification of those that are described in an Infobox or Chembox along with a Simplified Molecular-Input Line-Entry system (SMILES) code. Using a Python script, all so-listed chemicals (16,243) in Wikipedia were identified and then sorted on the basis of their pageview rankings. Of the 16,243 chemicals, 846 (5.2%) belonged to controlled substances (United States Drug Enforcement Administration), WHO essential medicines, or the top 300 US drugs. These 846 chemicals received 220 million pageviews, which is 41.4% of the pageviews for all members of the Wikipedia chemical list. The number of chemicals described in the entire corpus of Wikipedia remains a tiny fraction of the <107 known chemicals. Much remains to be done to make the venerable literature and data of chemistry readily accessible. Regardless, identification of popular chemicals in this manner can be used to create selected databases, to tailor educational curricula, or to create targeted informational materials (such as safety brochures); such considerations of public demand are likely to engender corresponding widespread interest.}, journal={REPORTERS, MARKERS, DYES, NANOPARTICLES, AND MOLECULAR PROBES FOR BIOMEDICAL APPLICATIONS XII}, author={Cao, Yuru and Mehta, Hely and Norcross, Ann E. and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2020} } @article{donal f. o'shea_sommer_taniguchi_lindsey_2020, title={Crystal Structure of 1,9-Dibromo-5-phenyldipyrrin, Tetrapyrrole Synthesis Derivative and Free Base Ligand of BODIPY Building Blocks}, volume={36}, ISSN={["1883-3578"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85089361305&partnerID=MN8TOARS}, DOI={10.2116/xraystruct.36.21}, abstractNote={A free base ligand of a BODIPY building block, 1,9-dibromo-5-phenyldipyrrin (2), was synthesized. The crystal structure was determined by the single crustal X-ray diffraction method at 293 K. The compound crystallizes in a monoclinic system and was characterized as follows: P21/c, a = 9.94150(10), b = 15.8691(3), c = 10.2160(2)Å, β = 118.8050(6), Z = 4, V = 1412.28(4)Å3, Dcalcd = 1.778 g/cm3, Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values are 0.0266 and 0.0653, respectively, for all 2896 independent reflections.}, journal={X-RAY STRUCTURE ANALYSIS ONLINE}, author={Donal F. O'shea and Sommer, Roger D. and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2020}, month={Jul}, pages={21–22} } @article{magdaong_taniguchi_diers_niedzwiedzki_kirmaier_lindsey_bocian_holten_2020, title={Photophysical Properties and Electronic Structure of Zinc(II) Porphyrins Bearing 0-4 meso-Phenyl Substituents: Zinc Porphine to Zinc Tetraphenylporphyrin (ZnTPP)}, volume={124}, ISSN={["1520-5215"]}, url={https://doi.org/10.1021/acs.jpca.0c06841}, DOI={10.1021/acs.jpca.0c06841}, abstractNote={Six zinc(II) porphyrins bearing 0-4 meso-phenyl substituents have been examined spectroscopically and theoretically. Comparisons with previously examined free base analogues afford a deep understanding of the electronic and photophysical effects of systematic addition of phenyl groups in porphyrins containing a central zinc(II) ion versus two hydrogen atoms. Trends in the wavelengths and relative intensities of the absorption bands are generally consistent with predictions from time-dependent density functional theory calculations and simulations from Gouterman's four-orbital model. These trends derive from a preferential effect of the meso-phenyl groups to raise the energy of the highest occupied molecular orbital. The calculations reveal additional insights, such as a progressive increase in oscillator strength in the violet-red (B-Q) absorption manifold with increasing number of phenyls. Progressive addition of 0-4 phenyl substituents to the zinc porphyrins in O2-free toluene engenders a reduction in the measured lifetime of the lowest singlet excited state (2.5-2.1 ns), an increase in the S1 → S0 fluorescence yield (0.022-0.030), a decrease in the yield of S1 → T1 intersystem crossing (0.93-0.88), and an increase in the yield of S1 → S0 internal conversion (0.048-0.090). The derived rate constants for S1 decay reveal significant differences in the photophysical properties of the zinc chelates versus free base forms. The unexpected finding of a larger rate constant for internal conversion for zinc chelates versus free bases is particularly exemplary. Collectively, the findings afford fundamental insights into the photophysical properties and electronic structure of meso-phenylporphyrins, which are widely used as benchmarks for tetrapyrrole-based architectures in solar energy and life sciences research.}, number={38}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, publisher={American Chemical Society (ACS)}, author={Magdaong, Nikki Cecil M. and Taniguchi, Masahiko and Diers, James R. and Niedzwiedzki, Dariusz M. and Kirmaier, Christine and Lindsey, Jonathan S. and Bocian, David F. and Holten, Dewey}, year={2020}, month={Sep}, pages={7776–7794} } @article{matsumoto_taniguchi_lindsey_2020, title={Bioconjugatable synthetic chlorins rendered water-soluble with three PEG-12 groups via click chemistry}, volume={24}, ISSN={["1099-1409"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85072584806&partnerID=MN8TOARS}, DOI={10.1142/S1088424619501219}, abstractNote={ Chlorins provide many ideal features for use as red-region fluorophores but require molecular tailoring for solubilization in aqueous solution. A chlorin building-block bearing 18,18-dimethyl, 15-bromo and 10-[2,4,6-tris(propargyloxy)phenyl] substituents has been transformed via click chemistry with CH3(OCH2CH[Formula: see text]-N3 followed by Suzuki coupling with 3-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)propanoic acid, thereby installing a water-solubilization motif and a bioconjugatable handle, respectively. In toluene, [Formula: see text]-dimethylformamide (DMF) or water, the resulting facially encumbered free base chlorin exhibits characteristic chlorin absorption ([Formula: see text] [Formula: see text]412, 643 nm) and fluorescence ([Formula: see text] [Formula: see text]645 nm) spectra with only modest variation in fluorescence quantum yield ([Formula: see text] values (0.24, 0.25 and 0.19, respectively). The zinc chlorin derived therefrom exhibits similar spectral constancy ([Formula: see text] [Formula: see text]414 and 613 nm, [Formula: see text] [Formula: see text]616 nm) and [Formula: see text] 0.094, 0.10 and 0.086 in the three solvents. The results together indicate the viability of the molecular design and synthetic methodology to create red-region fluorophores for use in diverse applications. }, number={1-3}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, author={Matsumoto, Nobuyuki and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2020}, pages={362–378} } @article{guo_xu_norcross_taniguchi_lindsey_2019, title={Developing a user community in the photosciences: a website for spectral data and access to PhotochemCAD}, volume={10893}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85073786008&partnerID=MN8TOARS}, DOI={10.1117/12.2508077}, abstractNote={A new website, centered on absorption and fluorescence spectra, has been designed for the broad community of members in the photosciences. Spectral data lie at the heart of the vast field of the photosciences, yet collections of such data are sparse, scattered and often in print rather than digital form. Because many if not most searches for photochemical data begin with individual spectra, the website should constitute a photosciences nexus. The database of <500 spectra can be accessed via text or by viewing molecular structures. The spectral data on the website are identical with those in the database associated with the software program PhotochemCAD, but only the latter contains the rich trove of companion references to the originating scientific literature. PhotochemCAD, which contains modules for diverse calculations germane to the photosciences, can be freely downloaded from the new website. To develop a community of users in the photosciences, a curated and validated set of email addresses of photoscientists has been generated from the primary photochemistry literature since 2004. The literature surveyed (19 journals, <45,000 articles) encompasses the flagship publications of 15 scholarly societies. The present work represents a step toward fulfilling the long-term ambition of assembling all known spectral data worldwide, from print and digital sources, in one carefully curated collection of digital data in a readily accessible site. The advances should broaden awareness and increase availability of spectra for diverse studies in the field of photosciences, which encompasses art, astrobiology, biology, chemistry, ecology, engineering, medicine, physics, textiles, and zoochromy.}, journal={REPORTERS, MARKERS, DYES, NANOPARTICLES, AND MOLECULAR PROBES FOR BIOMEDICAL APPLICATIONS XI}, publisher={SPIE}, author={Guo, Yaxue and Xu, Zhen and Norcross, Ann Elizabeth and Taniguchi, Masahiko and Lindsey, Jonathan S.}, editor={Achilefu, Samuel and Raghavachari, RameshEditors}, year={2019} } @article{qi_taniguchi_lindsey_2019, title={Heuristics from Modeling of Spectral Overlap in Forster Resonance Energy Transfer (FRET)}, volume={59}, ISSN={["1549-960X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85062087853&partnerID=MN8TOARS}, DOI={10.1021/acs.jcim.8b00753}, abstractNote={Among the photophysical parameters that underpin Förster resonance energy transfer (FRET), perhaps the least explored is the spectral overlap term ( J). While by definition J increases linearly with acceptor molar absorption coefficient (ε(A) in M-1 cm-1), is proportional to wavelength (λ4), and depends on the degree of overlap of the donor fluorescence and acceptor absorption spectra, the question arose as to the value of J for the case of perfect spectral overlap versus that for representative fluorophores with incomplete spectral overlap. Here, Gaussian distributions of absorption and fluorescent spectra have been modeled that encompass varying degrees of overlap, full-width-at-half-maximum (fwhm), and Stokes shift. For ε(A) = 105 M-1 cm-1 and perfect overlap, the J value (in M-1 cm-1 nm4) ranges from 1.15 × 1014 (200 nm) to 7.07 × 1016 (1000 nm), is almost linear with λ4 (average of λabs and λflu), and is nearly independent of fwhm. For visible-region fluorophores with perfectly overlapped Gaussian spectra, the resulting value of J ( JG-0) is ∼0.71 ε(A)λ4 (M-1 cm-1 nm4). The experimental J values for homotransfer, as occurs in light-harvesting antennas, were calculated with spectra from a static database of 60 representative compounds (12 groups, 5 compounds each) and found to range from 4.2 × 1010 ( o-xylene) to 5.3 × 1016 M-1 cm-1 nm4 (a naphthalocyanine). The degree of overlap, defined by the ratio of the experimental J to the model JG-0 for perfectly overlapped spectra, ranges from ∼0.5% (coumarin 151) to 77% (bacteriochlorophyll a). The results provide insights into how a variety of factors affect the resulting J values. The high degree of spectral overlap for (bacterio)chlorophylls prompts brief conjecture concerning the relevance of energy transfer to the question "why chlorophyll".}, number={2}, journal={JOURNAL OF CHEMICAL INFORMATION AND MODELING}, author={Qi, Qi and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2019}, month={Feb}, pages={652–667} } @article{taniguchi_hu_liu_du_lindsey_2018, title={Red and near-infrared fluorophores inspired by chlorophylls. Consideration of practical brightness in multicolor flow cytometry and biomedical sciences}, volume={10508}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85047458937&partnerID=MN8TOARS}, DOI={10.1117/12.2302709}, abstractNote={Demands in flow cytometry for increased multiplexing (for detection of multiple antigens) and brightness (for detection of rare entities) require new fluorophores (i.e., “colors”) with spectrally distinct fluorescence outside the relatively congested visible spectral region. Flow cytometry fluorophores typically must function in aqueous solution upon bioconjugation and ideally should exhibit a host of photophysical features: (i) strong absorption, (ii) sizable Stokes shift, (iii) modest if not strong fluorescence, and (iv) narrow fluorescence band. Tandem dyes have long been pursued to achieve a large effective Stokes shift, increased brightness, and better control over the excitation and emission wavelengths. Here, the attractive photophysical features of chlorophylls and bacteriochlorophylls – Nature’s chosen photoactive pigments for photosynthesis – are described with regards to use in flow cytometry. A chlorophyll (or bacteriochlorophyll) constitutes an intrinsic tandem dye given the red (or near-infrared) fluorescence upon excitation in the higher energy ultraviolet (UV) or visible absorption bands (due to rapid internal conversion to the lowest energy state). Synthetic (bacterio)chlorins are available with strong absorption (near-UV molar absorption coefficient ε(λexc) ~105 M-1cm-1), modest fluorescence quantum yield (Φf = 0.05–0.30), and narrow fluorescence band (10–25 nm) tunable from 600–900 nm depending on synthetic design. The “relative practical brightness” is given by intrinsic brightness [ε(λexc) x Φf] times ηf, the fraction of the fluorescence band that is captured by an emission filter in a multicolor experiment. The spectroscopic features of (bacterio)chlorins are evaluated quantitatively to illustrate practical brightness for this novel class of fluorophores in a prospective 8-color panel.}, journal={REPORTERS, MARKERS, DYES, NANOPARTICLES, AND MOLECULAR PROBES FOR BIOMEDICAL APPLICATIONS X}, publisher={SPIE}, author={Taniguchi, Masahiko and Hu, Gongfang and Liu, Rui and Du, Hai and Lindsey, Jonathan S.}, editor={Achilefu, Samuel and Raghavachari, RameshEditors}, year={2018} } @article{taniguchi_lindsey_2018, title={Database of Absorption and Fluorescence Spectra of > 300 Common Compounds for use in PhotochemCAD}, volume={94}, ISSN={["1751-1097"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85041842097&partnerID=MN8TOARS}, DOI={10.1111/php.12860}, abstractNote={AbstractThe design of new molecules for photochemical studies typically requires knowledge of spectral features of pertinent chromophores beginning with the absorption spectrum (λabs) and accompanying molar absorption coefficient (ε, m−1 cm−1) and often extending to the fluorescence spectrum (λem) and fluorescence quantum yield (Φf), where the fluorescence properties may be of direct relevance or useful as proxies to gain insight into the nature of the first excited singlet state. PhotochemCAD databases, developed over a period of 30 years, are described here. The previous databases for 150 compounds have been expanded to encompass 339 compounds for which absorption spectra (including ε values), fluorescence spectra (including Φf values) and references to the primary literature have been included where available (552 spectra altogether). The compounds exhibit spectra in the ultraviolet, visible and/or near‐infrared spectral regions. The compound classes and number of members include acridines (21), aromatic hydrocarbons (41), arylmethane dyes (11), azo dyes (18), biomolecules (18), chlorins/bacteriochlorins (16), coumarins (14), cyanine dyes (19), dipyrrins (7), heterocycles (26), miscellaneous dyes (13), oligophenylenes (13), oligopyrroles (6), perylenes (5), phthalocyanines (11), polycyclic aromatic hydrocarbons (16), polyenes/polyynes (10), porphyrins (34), quinones (24) and xanthenes (15). A database of 31 solar spectra also is included.}, number={2}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, publisher={Wiley}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2018}, pages={290–327} } @article{maher_passard_dogutan_halbach_anderson_gagliardi_taniguchi_lindsey_nocera_2017, title={Hydrogen Evolution Catalysis by a Sparsely Substituted Cobalt Chlorin}, volume={7}, ISSN={["2155-5435"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85021076592&partnerID=MN8TOARS}, DOI={10.1021/acscatal.7b00969}, abstractNote={A sparsely substituted chlorin macrocycle containing a Co(II) center (1-Co) has been synthesized and structurally characterized. The Co(II) atom resides in a square planar coordination environment and induces significant out-of-plane distortion of the chlorin macrocycle. The paramagnetic Co(II) center resides in the macrocycle in a S = 1/2 spin state, which displays an axial doublet signal (g⊥ ≈ 2.3 and g∥ ≈ 2.03) in the X-band EPR spectrum. The open-shell d-orbital configuration is manifest in the transient absorption spectrum, which reveals an excited-state lifetime of 8.6 ± 0.2 ps for 1-Co. The Co(II) chlorin exhibits a rich oxidation–reduction chemistry with five reversible one-electron waves (three oxidative processes and two reductive processes) observed in the cyclic voltammogram. The reduction processes of 1-Co drive hydrogen evolution catalysis. Electrochemical kinetics analysis of HER by 1-Co in trifluoroacetic acid reveals a hydrogen evolution mechanism that proceeds by an ECEC mechanism. Bench...}, number={5}, journal={ACS CATALYSIS}, publisher={American Chemical Society (ACS)}, author={Maher, Andrew G. and Passard, Guillaume and Dogutan, Dilek K. and Halbach, Robert L. and Anderson, Bryce L. and Gagliardi, Christopher J. and Taniguchi, Masahiko and Lindsey, Jonathan S. and Nocera, Daniel G.}, year={2017}, month={May}, pages={3597–3606} } @article{taniguchi_du_lindsey_2018, title={PhotochemCAD 3: Diverse Modules for Photophysical Calculations with Multiple Spectral Databases}, volume={94}, ISSN={["1751-1097"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85041847837&partnerID=MN8TOARS}, DOI={10.1111/php.12862}, abstractNote={AbstractThe PhotochemCAD program, developed over 30 years, is described comprehensively with focus on features of the most recent version (PhotochemCAD 3). The program is equipped with a streamlined user interface and provisions for handling multiple spectral databases. Eight modules enable calculations to be performed on the basis of the spectra in the databases. The calculational modules provide results concerning properties of individual compounds (oscillator strength, transition dipole moment, natural radiative lifetime), interactions of multiple compounds (Förster energy transfer, Dexter energy transfer, analysis of energy transfer among an array of chromophores) and composition of mixtures (multicomponent analysis). Synthetic spectra (blackbody radiator, Gaussian and Lorentzian curves, delta functions) also can be generated. For comparison and calculation, synthetic and experimental spectra can be shifted along both coordinate axes and combined by addition, subtraction and use of multiplicative factors. The core databases (described in the companion paper) have been expanded to 339 compounds for which absorption spectra (including molar absorption coefficient, ε), fluorescence spectra (including fluorescence quantum yield, Φf) and references to the primary literature have been included where available (552 spectra altogether). A database of 31 solar spectra also is included. Each calculational module is described along with illustrative examples.}, number={2}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, publisher={Wiley}, author={Taniguchi, Masahiko and Du, Hai and Lindsey, Jonathan S.}, year={2018}, pages={277–289} } @article{reddy_zhang_kim_mass_taniguchi_lindsey_2017, title={Synthesis and Spectral Properties of meso-Arylbacteriochlorins, Including Insights into Essential Motifs of their Hydrodipyrrin Precursors}, volume={22}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85020212586&partnerID=MN8TOARS}, DOI={10.3390/molecules22040634}, abstractNote={Synthetic bacteriochlorins—analogues of bacteriochlorophylls, Nature’s near-infrared absorbers—are attractive for diverse photochemical studies. meso-Arylbacteriochlorins have been prepared by the self-condensation of a dihydrodipyrrin–carbinol or dihydrodipyrrin–acetal following an Eastern-Western (E-W) or Northern-Southern (N-S) joining process. The bacteriochlorins bear a gem-dimethyl group in each pyrroline ring to ensure stability toward oxidation. The two routes differ in the location of the gem-dimethyl group at the respective 3- or 2-position in the dihydrodipyrrin, and the method of synthesis of the dihydrodipyrrin. Treatment of a known 3,3-dimethyldihydrodipyrrin-1-carboxaldehyde with an aryl Grignard reagent afforded the dihydrodipyrrin-1-(aryl)carbinol, and upon subsequent acetylation, the corresponding dihydrodipyrrin-1-methyl acetate (dihydrodipyrrin–acetate). Self-condensation of the dihydrodipyrrin–acetate gave a meso-diarylbacteriochlorin (E-W route). A 2,2-dimethyl-5-aryldihydrodipyrrin-1-(aryl)carbinol underwent self-condensation to give a trans-A2B2-type meso-tetraarylbacteriochlorin (N-S route). In each case, the aromatization process entails a 2e−/2H+ (aerobic) dehydrogenative oxidation following the dihydrodipyrrin self-condensation. Comparison of a tetrahydrodipyrrin–acetal (0%) versus a dihydrodipyrrin–acetal (41%) in bacteriochlorin formation and results with various 1-substituted dihydrodipyrrins revealed the importance of resonance stabilization of the reactive hydrodipyrrin intermediate. Altogether 10 new dihydrodipyrrins and five new bacteriochlorins have been prepared. The bacteriochlorins exhibit characteristic bacteriochlorophyll-like absorption spectra, including a Qy band in the region 726–743 nm.}, number={4}, journal={Molecules}, publisher={MDPI AG}, author={Reddy, Muthyala and Zhang, Shaofei and Kim, Han-Je and Mass, Olga and Taniguchi, Masahiko and Lindsey, Jonathan}, year={2017}, month={Apr}, pages={634} } @article{liu_chen_hood_taniguchi_diers_bocian_holten_lindsey_2017, title={Synthesis, photophysics and electronic structure of oxobacteriochlorins}, volume={41}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85022033561&partnerID=MN8TOARS}, DOI={10.1039/c6nj04135c}, abstractNote={Synthetic oxobacteriochlorins exhibit strong absorption in the deep-red window flanked by chlorins to the red and bacteriochlorins to the near-infrared.}, number={10}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Liu, Mengran and Chen, Chih-Yuan and Hood, Don and Taniguchi, Masahiko and Diers, James R. and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2017}, month={May}, pages={3732–3744} } @article{zhang_jiang_liu_taniguchi_mandal_evans-storms_pitner_bocian_holten_lindsey_2016, title={Bioconjugatable, PEGylated hydroporphyrins for photochemistry and photomedicine. Narrow-band, near-infrared-emitting bacteriochlorins}, volume={40}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84984904482&partnerID=MN8TOARS}, DOI={10.1039/c6nj01155a}, abstractNote={PEGylated bacteriochlorins are soluble in water, can be excited in the ultraviolet, and exhibit a narrow fluorescence band in the NIR spectral region.}, number={9}, journal={NEW JOURNAL OF CHEMISTRY}, author={Zhang, Nuonuo and Jiang, Jianbing and Liu, Mengran and Taniguchi, Masahiko and Mandal, Amit Kumar and Evans-Storms, Rosemary B. and Pitner, J. Bruce and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2016}, pages={7750–7767} } @article{deans_taniguchi_chandrashaker_ptaszek_lindsey_2016, title={Complexity in structure-directed prebiotic chemistry. Reaction bifurcation from a beta-diketone in tetrapyrrole formation}, volume={40}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84979074707&partnerID=MN8TOARS}, DOI={10.1039/c6nj00545d}, abstractNote={An unsymmetrical β-diketone with δ-aminolevulinic acid affords both a “defective” and a “normal” pyrrole; upon combinatorial reaction the former terminates chain-growth of the latter on the path to tetrapyrrole macrocycles.}, number={7}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Deans, Richard M. and Taniguchi, Masahiko and Chandrashaker, Vanampally and Ptaszek, Marcin and Lindsey, Jonathan S.}, year={2016}, month={Jul}, pages={6434–6440} } @article{deans_taniguchi_chandrashaker_ptaszek_chambers_soares_lindsey_2016, title={Complexity in structure-directed prebiotic chemistry. Unexpected compositional richness from competing reactants in tetrapyrrole formation}, volume={40}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84979079544&partnerID=MN8TOARS}, DOI={10.1039/c6nj00543h}, abstractNote={Acyclic reactants afford “partially defective” pyrroles that interfere with chain growth of “normal” pyrroles on the path to tetrapyrrole macrocycles.}, number={7}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Deans, Richard M. and Taniguchi, Masahiko and Chandrashaker, Vanampally and Ptaszek, Marcin and Chambers, Dana R. and Soares, Ana R. M. and Lindsey, Jonathan S.}, year={2016}, month={Jul}, pages={6421–6433} } @article{mandal_taniguchi_diers_niedzwiedzki_kirmaier_lindsey_bocian_holten_2016, title={Photophysical Properties and Electronic Structure of Porphyrins Bearing Zero to Four meso-Phenyl Substituents: New Insights into Seemingly Well Understood Tetrapyrroles}, volume={120}, ISSN={["1089-5639"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85021654881&partnerID=MN8TOARS}, DOI={10.1021/acs.jpca.6b09483}, abstractNote={Six free base porphyrins bearing 0-4 meso substituents have been examined by steady-state and time-resolved absorption and fluorescence spectroscopy in both toluene and N,N-dimethylformamide (DMF). The lifetime of the lowest singlet excited state (S1) decreases with an increase in the number of meso-phenyl groups; the values in toluene are H2P-0 (15.5 ns) > H2P-1 (14.9 ns) > H2P-2c (14.4 ns) > H2P-2t (13.8 ns) ∼ H2P-3 (13.8 ns) > H2P-4 (12.8 ns), where "H2P" refers to the core free base porphyrin, the numerical suffix indicates the number of meso-phenyl groups, and "c" and "t" refer to cis and trans, respectively. The opposite trend is found for the fluorescence quantum yield; the values in toluene are H2P-0 (0.049) < H2P-1 (0.063) ∼ H2P-2c (0.063) < H2P-2t (0.071) < H2P-3 (0.073) < H2P-4 (0.090). Similar trends occur in DMF. All radiative and nonradiative (internal conversion and intersystem crossing) rate constants for S1 decay increase with the increasing number of meso-phenyl groups. The increase in the rate constant for fluorescence parallels an increase in oscillator strength of the S0 → S1 absorption manifold. The trend is reproduced by time-dependent density functional theory calculations. The calculations within the context of the four-orbital model reveal that the enhanced S0 ↔ S1 radiative probabilities derive from a preferential effect of the meso-phenyl groups to raise the energy of the highest occupied molecular orbital, which underpins a parallel bathochromic shift in the S0 → S1 absorption wavelength. Polarizations of the S1 and S2 excited states with respect to molecular structural features (e.g., the central proton axis) are analyzed in the context of historical conventions for porphyrins versus chlorins and bacteriochlorins, where some ambiguity exists, including for porphine, one of the simplest tetrapyrroles. Collectively, the study affords fundamental insights into the photophysical properties and electronic structure of meso-phenylporphyrins that should aid their continued widespread use as benchmarks for tetrapyrrole-based architectures in chemical, solar-energy, and life-sciences research.}, number={49}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Mandal, Amit Kumar and Taniguchi, Masahiko and Diers, James R. and Niedzwiedzki, Dariusz M. and Kirmaier, Christine and Lindsey, Jonathan S. and Bocian, David F. and Holten, Dewey}, year={2016}, month={Dec}, pages={9719–9731} } @article{taniguchi_deans_chandrashaker_ptaszek_lindsey_2016, title={Scope and limitations of two model prebiotic routes to tetrapyrrole macrocycles}, volume={40}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84984911595&partnerID=MN8TOARS}, DOI={10.1039/c6nj01423b}, abstractNote={Aqueous reaction (35 °C, 72 h) of two acyclic compounds, an α-aminoketone + β-ketoester or β-diketone (not shown), affords a pyrrole that self-condenses to give the porphyrinogen.}, number={9}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Taniguchi, Masahiko and Deans, Richard M. and Chandrashaker, Vanampally and Ptaszek, Marcin and Lindsey, Jonathan S.}, year={2016}, pages={7445–7455} } @article{chandrashaker_ptaszek_taniguchi_lindsey_2016, title={Synthesis of diverse acyclic precursors to pyrroles for studies of prebiotic routes to tetrapyrrole macrocycles}, volume={40}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84990050463&partnerID=MN8TOARS}, DOI={10.1039/c6nj02048h}, abstractNote={Some 50 ketones, β-diketones, β-ketoesters and α-aminoketones have been prepared for studies of the formation of trisubstituted pyrroles equipped for self-condensation leading to tetrapyrrole macrocycles.}, number={10}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Chandrashaker, Vanampally and Ptaszek, Marcin and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2016}, pages={8786–8808} } @misc{taniguchi_lindsey_2017, title={Synthetic Chlorins, Possible Surrogates for Chlorophylls, Prepared by Derivatization of Porphyrins}, volume={117}, ISSN={["1520-6890"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85010748506&partnerID=MN8TOARS}, DOI={10.1021/acs.chemrev.5b00696}, abstractNote={Chlorophylls make Earth green, are the central constituents in the engine of photosynthesis, and not surprisingly have garnered immense attention. A chlorin, the core chromophore of a chlorophyll, is a dihydroporphyrin macrocycle that contains one pyrroline ring and three pyrrole rings. The dominant method for the synthesis of chlorins has entailed the derivatization of porphyrins. The present review covers the ostensibly simple conversion of porphyrins, regardless of synthetic or biological origin, to chlorins. The period covered encompasses the entire history since the beginnings of chlorin synthetic chemistry in the early 20th century through 2015. Representative transformations include hydrogenation, cycloaddition, annulation, and diverse "breaking and mending" approaches. Altogether, the synthesis of >1000 chlorins or chlorin-like compounds (containing >50 distinct pyrroline motifs) is described. Such diversity animates the question "what structural features are essential for a chlorin to resemble chlorophyll?" To begin to address the structure-spectrum relationship, > 250 absorption spectra are provided for representative structures. The synthesis and spectral properties of the vast collection of compounds described herein are expected to illuminate the scope to which synthetic chlorins can serve as surrogates for chlorophylls and be exploited in diverse ways.}, number={2}, journal={CHEMICAL REVIEWS}, publisher={American Chemical Society (ACS)}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2017}, month={Jan}, pages={344–535} } @article{taniguchi_ptaszek_chandrashaker_lindsey_2017, title={The Porphobilinogen Conundrum in Prebiotic Routes to Tetrapyrrole Macrocycles}, volume={47}, ISSN={["1573-0875"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84969780645&partnerID=MN8TOARS}, DOI={10.1007/s11084-016-9506-1}, abstractNote={Attempts to develop a credible prebiotic route to tetrapyrroles have relied on enzyme-free recapitulation of the extant biosynthesis, but this process has foundered from the inability to form the pyrrole porphobilinogen (PBG) in good yield by self-condensation of the precursor δ-aminolevulinic acid (ALA). PBG undergoes robust oligomerization in aqueous solution to give uroporphyrinogen (4 isomers) in good yield. ALA, PBG, and uroporphyrinogen III are universal precursors to all known tetrapyrrole macrocycles. The enzymic formation of PBG entails carbon-carbon bond formation between the less stable enolate/enamine of one ALA molecule (3-position) and the carbonyl/imine (4-position) of the second ALA molecule; without enzymes, the first ALA reacts at the more stable enolate/enamine (5-position) and gives the pyrrole pseudo-PBG. pseudo-PBG cannot self-condense, yet has one open α-pyrrole position and is proposed to be a terminator of oligopyrromethane chain-growth from PBG. Here, 23 analogues of ALA have been subjected to density functional theoretical (DFT) calculations, but no motif has been identified that directs reaction at the 3-position. Deuteriation experiments suggested 5-(phosphonooxy)levulinic acid would react preferentially at the 3- versus 5-position, but a hybrid condensation with ALA gave no observable uroporphyrin. The results suggest efforts toward a biomimetic, enzyme-free route to tetrapyrroles from ALA should turn away from structure-directed reactions and focus on catalysts that orient the two aminoketones to form PBG in a kinetically controlled process, thereby avoiding formation of pseudo-PBG.}, number={1}, journal={ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES}, publisher={Springer Nature}, author={Taniguchi, Masahiko and Ptaszek, Marcin and Chandrashaker, Vanampally and Lindsey, Jonathan S.}, year={2017}, month={Mar}, pages={93–119} } @article{deans_chandrashaker_taniguchi_lindsey_2015, title={Complexity in structure-directed prebiotic chemistry. Effect of a defective competing reactant in tetrapyrrole formation}, volume={39}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84945937304&partnerID=MN8TOARS}, DOI={10.1039/c5nj01474c}, abstractNote={A reactive but defective pyrrole, derived from the simple β-diketone acetylacetone, terminates chain-growth in a quantitative combinatorial manner in tetrapyrrole formation.}, number={11}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Deans, Richard M. and Chandrashaker, Vanampally and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2015}, pages={8273–8281} } @article{zhang_reddy_jiang_taniguchi_sommer_lindsey_2015, title={Elaboration of an unexplored substitution site in synthetic bacteriochlorins}, volume={19}, ISSN={["1099-1409"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84937975805&partnerID=MN8TOARS}, DOI={10.1142/s1088424615500534}, abstractNote={ The ability to introduce substituents at designated sites about the perimeter of synthetic bacteriochlorins – analogs of bacteriochlorophylls of bacterial photosynthesis – remains a subject of ongoing study. Here, the self-condensation of a dihydrodipyrrin-dioxolane affords a 5-[2-(trimethylsiloxy)ethoxy]bacteriochlorin. Like a 5-methoxybacteriochlorin, the latter undergoes regioselective bromination at the 15-position, directed by the distal 5-alkoxy group. On the other hand, attempted bromination of a bacteriochlorin bearing a 5-(2-hydroxyethoxy) group resulted in intramolecular ether formation with the adjacent β-pyrroline position to give an annulated dioxepine ring (confirmed by single-crystal X-ray structural analysis). The hydroxyethoxy group at the 5-position can be derivatized by acylation. In addition, the installation of auxochromes (methoxycarbonyl, phenylethynyl) at the β-pyrrole rings causes a substantial bathochromic shift of the long-wavelength absorption band (812 nm) and companion fluorescence emission band (821 nm). Taken together, the modification of the 5-substituent complements existing methods for installing a single substituent on the bacteriochlorin macrocycle. }, number={7}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, publisher={World Scientific Pub Co Pte Lt}, author={Zhang, Nuonuo and Reddy, Kanumuri Ramesh and Jiang, Jianbing and Taniguchi, Masahiko and Sommer, Roger D. and Lindsey, Jonathan S.}, year={2015}, month={Jul}, pages={887–902} } @article{vairaprakash_yang_sahin_taniguchi_krayer_diers_wang_niedzwiedzki_kirmaier_lindsey_et al._2015, title={Extending the Short and Long Wavelength Limits of Bacteriochlorin Near-Infrared Absorption via Dioxo- and Bisimide-Functionalization}, volume={119}, ISSN={["1520-6106"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84925935682&partnerID=MN8TOARS}, DOI={10.1021/jp512818g}, abstractNote={Six new bacteriochlorins expanding the range of the strong near-infrared (NIR) absorption (Qy band) to both shorter and longer wavelengths (∼690 to ∼900 nm) have been synthesized and characterized. The architectures include bacteriochlorin-bisimides that have six-membered imide rings spanning the 3,5- and 13,15-macrocycle positions or five-membered imide rings spanning the β-pyrrolic 2,3- and 12,13-positions. Both bisimide types absorb at significantly longer wavelength than the bacteriochlorin precursors (no fused rings), whereas oxo-groups at the 7- or 7,17-positions shift the Qy band to a new short wavelength limit. Surprisingly, bacteriochlorin-bisimides with five-membered β-pyrrolic-centered imide rings have a Qy band closer to that of six-membered bacteriochlorin-monoimides. However, the five-membered bisimides (versus the six-membered bacteriochlorin-monoimides) have significantly enhanced absorption intensity that is paralleled by an ∼2-fold higher fluorescence yield (∼0.16 vs ∼0.07) and longer singlet excited-state lifetime (∼4 ns vs ∼2 ns). The photophysical enhancements derive in part from mixing of the lowest unoccupied frontier molecular orbitals of the five-membered imide ring with those of the bacteriochlorin framework. In general, all of the new bacteriochlorins have excited-state lifetimes (1-4 ns) that are sufficiently long for use in molecular-based systems for photochemical applications.}, number={12}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Vairaprakash, Pothiappan and Yang, Eunkyung and Sahin, Tuba and Taniguchi, Masahiko and Krayer, Michael and Diers, James R. and Wang, Alfred and Niedzwiedzki, Dariusz M. and Kirmaier, Christine and Lindsey, Jonathan S. and et al.}, year={2015}, month={Mar}, pages={4382–4395} } @article{yang_zhang_krayer_taniguchi_diers_kirmaier_lindsey_bocian_holten_2016, title={Integration of Cyanine, Merocyanine and Styryl Dye Motifs with Synthetic Bacteriochlorins}, volume={92}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84955342215&partnerID=MN8TOARS}, DOI={10.1111/php.12547}, abstractNote={AbstractUnderstanding the effects of substituents on spectral properties is essential for the rational design of tailored bacteriochlorins for light‐harvesting and other applications. Toward this goal, three new bacteriochlorins containing previously unexplored conjugating substituents have been prepared and characterized. The conjugating substituents include two positively charged species, 2‐(N‐ethyl 2‐quinolinium)vinyl‐ (B‐1) and 2‐(N‐ethyl 4‐pyridinium)vinyl‐ (B‐2), and a neutral group, acroleinyl‐ (B‐3); the charged species resemble cyanine (or styryl) dye motifs whereas the neutral unit resembles a merocyanine dye motif. The three bacteriochlorins are examined by static and time‐resolved absorption and emission spectroscopy and density functional theoretical calculations. B‐1 and B‐2 have Qy absorption bathochromically shifted well into the NIR region (822 and 852 nm), farther than B‐3 (793 nm) and other 3,13‐disubstituted bacteriochlorins studied previously. B‐1 and B‐2 have broad Qy absorption and fluorescence features with large peak separation (Stokes shift), low fluorescence yields, and shortened S1 (Qy) excited‐state lifetimes (~700 ps and ~100 ps). More typical spectra and S1 lifetime (~2.3 ns) are found for B‐3. The combined photophysical and molecular‐orbital characteristics suggest the altered spectra and enhanced nonradiative S1 decay of B‐1 and B‐2 derive from excited‐state configurations in which electron density is shifted between the macrocycle and the substituents.}, number={1}, journal={Photochemistry and Photobiology}, publisher={Wiley}, author={Yang, Eunkyung and Zhang, Nuonuo and Krayer, Michael and Taniguchi, Masahiko and Diers, James R. and Kirmaier, Christine and Lindsey, Jonathan S. and Bocian, David F. and Holten, Dewey}, year={2016}, pages={111–125} } @article{jiang_taniguchi_lindsey_2015, title={Near-infrared tunable bacteriochlorins equipped for bioorthogonal labeling}, volume={39}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84930627951&partnerID=MN8TOARS}, DOI={10.1039/c5nj00209e}, abstractNote={Nine new near-infrared absorbing (729–820 nm) synthetic bacteriochlorins are equipped with one of four reactive groups for bioorthogonal conjugation.}, number={6}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Jiang, Jianbing and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2015}, pages={4534–4550} } @article{alexy_hintz_hughes_taniguchi_lindsey_2015, title={Paley's watchmaker analogy and prebiotic synthetic chemistry in surfactant assemblies. Formaldehyde scavenging by pyrroles leading to porphyrins as a case study}, volume={13}, ISSN={["1477-0539"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84942899459&partnerID=MN8TOARS}, DOI={10.1039/c5ob01409c}, abstractNote={Facile exchange of micromolar dialkylpyrrolic constituents among a Poisson distribution of aqueous micelles overcomes immense statistical odds against reaction.}, number={39}, journal={ORGANIC & BIOMOLECULAR CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Alexy, Eric J. and Hintz, Carl W. and Hughes, Hubert M. and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2015}, pages={10025–10031} } @article{faries_diers_springer_yang_ptaszek_lahaye_krayer_taniguchi_kirmaier_lindsey_et al._2015, title={Photophysical Properties and Electronic Structure of Chlorin-Imides: Bridging the Gap between Chlorins and Bacteriochlorins}, volume={119}, ISSN={["1520-5207"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84934319596&partnerID=MN8TOARS}, DOI={10.1021/jp511257w}, abstractNote={Efficient light harvesting for molecular-based solar-conversion systems requires absorbers that span the photon-rich red and near-infrared (NIR) regions of the solar spectrum. Reported herein are the photophysical properties of a set of six chlorin-imides and nine synthetic chlorin analogues that extend the absorption deeper (624-714 nm) into these key spectral regions. These absorbers help bridge the gap between typical chlorins and bacteriochlorins. The new compounds have high fluorescence quantum yields (0.15-0.34) and long singlet excited-state lifetimes (4.2-10.9 ns). The bathochromic shift in Qy absorption is driven by substituent-based stabilization of the lowest unoccupied molecular orbital, with the largest shifts for chlorins that bear an electron-withdrawing, conjugative group at the 3-position in combination with a 13,15-imide ring.}, number={24}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Faries, Kaitlm M. and Diers, James R. and Springer, Joseph W. and Yang, Eunkyung and Ptaszek, Marcin and Lahaye, Dorothee and Krayer, Michael and Taniguchi, Masahiko and Kirmaier, Christine and Lindsey, Jonathan S. and et al.}, year={2015}, month={Jun}, pages={7503–7515} } @article{ra_gauger_muthukumaran_balasubramanian_chandrashaker_taniguchi_yu_talley_ehudin_ptaszek_et al._2015, title={Progress towards synthetic chlorins with graded polarity, conjugatable substituents, and wavelength tunability}, volume={19}, ISSN={["1099-1409"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85027922166&partnerID=MN8TOARS}, DOI={10.1142/s1088424615500042}, abstractNote={ Advances in chlorin synthetic chemistry now enable the de novo preparation of diverse chlorin-containing molecular architectures. Five distinct molecular designs have been explored here, including hydrophobic bioconjugatable (oxo)chlorins; a hydrophilic bioconjugatable chlorin; a trans-ethynyl/iodochlorin building block; a set of chlorins bearing electron-rich (methoxy, dimethylamino, methylthio) groups at the 3-position; and a set of ten 3,13-disubstituted chlorins chiefly bearing groups with extended π-moieties. Altogether 23 new chlorins (17 targets, 6 intermediates) have been prepared. The challenge associated with molecular designs that encompass the combination of "hydrophilic, bioconjugatable and wavelength-tunable" chiefly resides in the nature of the hydrophilic unit. }, number={4}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, publisher={World Scientific Pub Co Pte Lt}, author={Ra, Doyoung and Gauger, Kelly A. and Muthukumaran, Kannan and Balasubramanian, Thiagarajan and Chandrashaker, Vanampally and Taniguchi, Masahiko and Yu, Zhanqian and Talley, Daniel C. and Ehudin, Melanie and Ptaszek, Marcin and et al.}, year={2015}, month={Apr}, pages={547–572} } @article{chen_taniguchi_lindsey_2014, title={NMR spectral properties of 16 synthetic bacteriochlorins with site-specific C-13 or N-15 substitution}, volume={18}, ISSN={["1099-1409"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903791617&partnerID=MN8TOARS}, DOI={10.1142/s1088424614500199}, abstractNote={ The 1 H , 13 C , and 15 N nuclear magnetic resonance (NMR) spectral properties have been examined of a family of synthetic bacteriochlorins wherein each member incorporates a pair of 13 C or 15 N atoms. The atom locations span the inner core of the macrocycle: (1) 15 N at the 21,23- or 22,24-positions; (2) 13 C at the meso- (5,15- or 10,20-) positions; (3) 13 C at the pyrrole α-positions (1,11- or 4,14-positions); and (4) 13 C at the pyrroline α-positions (6,16- or 9,19-positions). Each bacteriochlorin lacks peripheral substituents other than a geminal dimethyl group at the 8- and 18-positions to preclude adventitious dehydrogenation. In total, eight free base and eight zinc bacteriochlorin isotopologs were examined to directly assign 1 H , 13 C and 15 N resonances of the macrocycle skeleton. Complete and unambiguous assignments, including those for all tertiary and quaternary carbons, were accomplished chiefly by direct inspection of 1D NMR spectra of each isotopolog. Coupling constants (1 H –1 H , 13 C –1 H , 15 N –1 H , 13 C –13 C and 15 N –13 C ), which are rarely reported for tetrapyrroles, also were extracted. The 1 H and 13 C chemical shifts were then compared to those of unsaturated analogs (chlorin, porphyrin) and natural bacteriochlorophylls. The comprehensive set of NMR spectroscopic properties of sparsely substituted bacteriochlorins provides valuable information for understanding substitution effects and aromaticity in structurally more elaborate counterparts. }, number={6}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, publisher={World Scientific Pub Co Pte Lt}, author={Chen, Chih-Yuan and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2014}, month={Jun}, pages={433–456} } @article{springer_taniguchi_krayer_ruzié_diers_niedzwiedzki_bocian_lindsey_holten_2014, title={Photophysical properties and electronic structure of retinylidene–chlorin–chalcones and analogues}, volume={13}, ISSN={1474-905X 1474-9092}, url={http://dx.doi.org/10.1039/C3PP50421B}, DOI={10.1039/C3PP50421B}, abstractNote={Synthetic chlorins can accommodate diverse substituents about the macrocycle perimeter. Simple auxochromes ( e.g. , vinyl, acetyl, phenyl) allow systematic tuning of spectral and photophysical features. More extensive spectral tailoring may be achieved by using more potent, highly conjugated substituents that themselves bring new absorption into a target spectral region, if deleterious excited-state quenching processes can be avoided. To explore such an expanded substituent space, herein the spectral and photophysical properties of four chlorin–chalcones are reported. The molecules are free base and zinc chlorins with substituents at the 13-position that include a chalcone and an extended chalcone derived by reaction of the 13-acetylchlorin with benzaldehyde and all- trans -retinal, respectively. Measurements of the spectral and photophysical properties ( Φ _f, τ _s, k _f, k _ic, k _isc) are accompanied by density functional calculations that examine the characteristics of the frontier molecular orbitals. The chlorin–chalcones in nonpolar (toluene) and polar (dimethylsulfoxide) media exhibit bathochromically shifted (and intense) Q _y absorption bands. The presence of the retinylidene group adds new absorption in the blue-green region where the chlorins are typically transparent; excitation in this region leads to quantitative formation of the chlorin Q _y excited state. The spectral properties generally correlate with substituent effects on the frontier MOs. The four chlorin–chalcones in the solvent toluene have high fluorescence yields (0.24–0.30) and multi-nanosecond singlet excited-state lifetimes (3.7–8.4 ns), in addition to the added absorption imparted by the chalcone moiety. Collectively, the studies reported herein provide insight into the fundamental properties of chlorins and illustrate the utility of chalcones as a means of both tuning and augmenting the spectral properties of these chromophores.}, number={4}, journal={Photochemical & Photobiological Sciences}, publisher={Royal Society of Chemistry (RSC)}, author={Springer, Joseph W. and Taniguchi, Masahiko and Krayer, Michael and Ruzié, Christian and Diers, James R. and Niedzwiedzki, Dariusz M. and Bocian, David F. and Lindsey, Jonathan S. and Holten, Dewey}, year={2014}, pages={634} } @article{taniguchi_henry_cogdell_lindsey_2014, title={Statistical considerations on the formation of circular photosynthetic light-harvesting complexes from Rhodopseudomonas palustris}, volume={121}, ISSN={["1573-5079"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84902284652&partnerID=MN8TOARS}, DOI={10.1007/s11120-014-9975-x}, abstractNote={Depending on growth conditions, some species of purple photosynthetic bacteria contain peripheral light-harvesting (LH2) complexes that are heterogeneous owing to the presence of different protomers (containing different αβ-apoproteins). Recent spectroscopic studies of Rhodopseudomonas palustris grown under low-light conditions suggest the presence of a C 3-symmetric LH2 nonamer comprised of two distinct protomers. The software program Cyclaplex, which enables generation and data-mining of virtual libraries of molecular rings formed upon combinatorial reactions, has been used to delineate the possible number and type of distinct nonamers as a function of numbers of distinct protomers. The yield of the C 3-symmetric nonamer from two protomers (A and B in varying ratios) has been studied under the following conditions: (1) statistical, (2) enriched (preclusion of the B-B sequence), and (3) seeded (pre-formation of an A-B-A block). The yield of C 3-symmetric nonamer is at most 0.98 % under statistical conditions versus 5.6 % under enriched conditions, and can be dominant under conditions of pre-seeding with an A-B-A block. In summary, the formation of any one specific nonamer even from only two protomers is unlikely on statistical grounds but must stem from enhanced free energy of formation or a directed assembly process by as-yet unknown factors.}, number={1}, journal={PHOTOSYNTHESIS RESEARCH}, publisher={Springer Nature}, author={Taniguchi, Masahiko and Henry, Sarah and Cogdell, Richard J. and Lindsey, Jonathan S.}, year={2014}, month={Jul}, pages={49–60} } @article{harris_jiang_niedzwiedzki_jiao_taniguchi_kirmaier_loach_bocian_lindsey_holten_et al._2014, title={Versatile design of biohybrid light-harvesting architectures to tune location, density, and spectral coverage of attached synthetic chromophores for enhanced energy capture}, volume={121}, ISSN={["1573-5079"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84902249655&partnerID=MN8TOARS}, DOI={10.1007/s11120-014-9993-8}, abstractNote={Biohybrid antennas built upon chromophore-polypeptide conjugates show promise for the design of efficient light-capturing modules for specific purposes. Three new designs, each of which employs analogs of the β-polypeptide from Rhodobacter sphaeroides, have been investigated. In the first design, amino acids at seven different positions on the polypeptide were individually substituted with cysteine, to which a synthetic chromophore (bacteriochlorin or Oregon Green) was covalently attached. The polypeptide positions are at -2, -6, -10, -14, -17, -21, and -34 relative to the 0-position of the histidine that coordinates bacteriochlorophyll a (BChl a). All chromophore-polypeptides readily formed LH1-type complexes upon combination with the α-polypeptide and BChl a. Efficient energy transfer occurs from the attached chromophore to the circular array of 875 nm absorbing BChl a molecules (denoted B875). In the second design, use of two attachment sites (positions -10 and -21) on the polypeptide affords (1) double the density of chromophores per polypeptide and (2) a highly efficient energy-transfer relay from the chromophore at -21 to that at -10 and on to B875. In the third design, three spectrally distinct bacteriochlorin-polypeptides were prepared (each attached to cysteine at the -14 position) and combined in an ~1:1:1 mixture to form a heterogeneous mixture of LH1-type complexes with increased solar coverage and nearly quantitative energy transfer from each bacteriochlorin to B875. Collectively, the results illustrate the great latitude of the biohybrid approach for the design of diverse light-harvesting systems.}, number={1}, journal={PHOTOSYNTHESIS RESEARCH}, author={Harris, Michelle A. and Jiang, Jianbing and Niedzwiedzki, Dariusz M. and Jiao, Jieying and Taniguchi, Masahiko and Kirmaier, Christine and Loach, Paul A. and Bocian, David F. and Lindsey, Jonathan S. and Holten, Dewey and et al.}, year={2014}, month={Jul}, pages={35–48} } @article{soares_thanaiah_taniguchi_lindsey_2013, title={Aqueous–membrane partitioning of β-substituted porphyrins encompassing diverse polarity}, volume={37}, ISSN={1144-0546 1369-9261}, url={http://dx.doi.org/10.1039/c3nj41042k}, DOI={10.1039/c3nj41042k}, abstractNote={Understanding the partitioning of organic molecules between aqueous solution and lipid membranes is critical to problems in fields ranging from drug design to environmental science to studies of the origin of life. Here, six β-substituted porphyrins of diverse polarity were examined for partitioning between the membranes of phosphatidylcholine vesicles and aqueous solution. The porphyrins include uroporphyrin I (number of carboxylic acid substituents = 8), heptacarboxylic acid porphyrin I (7), hexacarboxylic acid porphyrin I (6), coproporphyrin I (4), mesoporphyrin IX (2) and etioporphyrin I (0). The porphyrins were examined individually and collectively. In each case, size-exclusion chromatography was used to separate a porphyrins/vesicles fraction and a porphyrins/aqueous fraction. Each fraction was analyzed quantitatively by reversed-phase HPLC with fluorescence detection or by UV-Visible absorption spectroscopy to give partition coefficients. The partition coefficients for the six porphyrins also were calculated (clog P) using seven software programs: ACD/Labs, ALOGPS 2.1, Chemdraw, Molinspiration, KowWin, MarvinSketch, and XLOGP3. For perspective, clog P values for seven other porphyrins and 18 non-porphyrins also were calculated. Wide variation among programs was observed for almost all of the porphyrins and non-porphyrins of similar molecular weight. The dearth of porphyrins with requisite substituent patterns for experimental examination and the unreliability of calculation preclude definitive predictions concerning partitioning of unknown porphyrins; however, the results afford heuristics to predict aqueous–membrane partitioning of diverse β-substituted porphyrins.}, number={4}, journal={New Journal of Chemistry}, publisher={Royal Society of Chemistry (RSC)}, author={Soares, Ana R. M. and Thanaiah, Yugaananthy and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2013}, pages={1087} } @article{taniguchi_lindsey_2013, title={ChemInform Abstract: Enumeration of Isomers of Substituted Tetrapyrrole Macrocycles: From Classical Problems in Biology to Modern Combinatorial Libraries}, volume={44}, DOI={10.1002/chin.201331277}, abstractNote={AbstractReview: 232 refs.}, number={31}, journal={ChemInform}, publisher={Wiley}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2013}, month={Jul}, pages={no-no} } @article{taniguchi_du_lindsey_2013, title={Enumeration of Virtual Libraries of Combinatorial Modular Macrocyclic (Bracelet, Necklace) Architectures and Their Linear Counterparts}, volume={53}, ISSN={["1549-960X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84883274376&partnerID=MN8TOARS}, DOI={10.1021/ci400175f}, abstractNote={A wide variety of cyclic molecular architectures are built of modular subunits and can be formed combinatorially. The mathematics for enumeration of such objects is well-developed yet lacks key features of importance in chemistry, such as specifying (i) the structures of individual members among a set of isomers, (ii) the distribution (i.e., relative amounts) of products, and (iii) the effect of nonequal ratios of reacting monomers on the product distribution. Here, a software program (Cyclaplex) has been developed to determine the number, identity (including isomers), and relative amounts of linear and cyclic architectures from a given number and ratio of reacting monomers. The program includes both mathematical formulas and generative algorithms for enumeration; the latter go beyond the former to provide desired molecular-relevant information and data-mining features. The program is equipped to enumerate four types of architectures: (i) linear architectures with directionality (macroscopic equivalent = electrical extension cords), (ii) linear architectures without directionality (batons), (iii) cyclic architectures with directionality (necklaces), and (iv) cyclic architectures without directionality (bracelets). The program can be applied to cyclic peptides, cycloveratrylenes, cyclens, calixarenes, cyclodextrins, crown ethers, cucurbiturils, annulenes, expanded meso-substituted porphyrin(ogen)s, and diverse supramolecular (e.g., protein) assemblies. The size of accessible architectures encompasses up to 12 modular subunits derived from 12 reacting monomers or larger architectures (e.g. 13-17 subunits) from fewer types of monomers (e.g. 2-4). A particular application concerns understanding the possible heterogeneity of (natural or biohybrid) photosynthetic light-harvesting oligomers (cyclic, linear) formed from distinct peptide subunits.}, number={9}, journal={JOURNAL OF CHEMICAL INFORMATION AND MODELING}, publisher={American Chemical Society (ACS)}, author={Taniguchi, Masahiko and Du, Hai and Lindsey, Jonathan S.}, year={2013}, month={Sep}, pages={2203–2216} } @article{soares_taniguchi_chandrashaker_lindsey_2013, title={Expanded combinatorial formation of porphyrin macrocycles in aqueous solution containing vesicles. A prebiotic model}, volume={37}, ISSN={1144-0546 1369-9261}, url={http://dx.doi.org/10.1039/c3nj41041b}, DOI={10.1039/c3nj41041b}, abstractNote={The role of combinatorial processes in the origin of life remains relatively unexplored. In a chemical model for the possible prebiogenesis of tetrapyrrole macrocycles reported previously, a tandem combinatorial reaction of two diones (substituents = methyl, acetic acid) and two aminoketones (substituents = ethyl, propanoic acid) afforded up to 538 porphyrins (upon oxidation of the corresponding porphyrinogens). The reaction was performed at a 1 : 1 ratio of hydrophobic and hydrophilic substituents in each pool of reactants, and the resulting porphyrins partitioned in ∼1 : 1 ratio between aqueous solution and phosphatidylcholine vesicle membranes. Here, a change in the ratio of hydrophobic and hydrophilic substituents of the [2 × 2] reaction gave corresponding changes in the polarity profile of the resulting porphyrins (3.5–9.0% yield). Reaction of four diones and four aminoketones (bearing hydrophilic or hydrophobic substituents) in the presence of lipid vesicles followed by photooxidation afforded porphyrins in 8.7% yield. The resulting porphyrins partitioned in ∼1 : 1 ratio between phosphatidylcholine vesicles and aqueous solution, as observed previously for the [2 × 2] reaction. Both the aqueous fraction and the vesicles fraction were photochemically active as evidenced by the fluorescence quantum yield (Φf ∼ 0.1). Software (PorphyrinViLiGe) for virtual library generation indicates that the [4 × 4] reaction affords up to 131 464 porphyrins. The relative insensitivity of physicochemical properties (partitioning, photoactivity) toward combinatorial expansion may be a valuable yet unappreciated attribute for prebiotic functionality.}, number={4}, journal={New Journal of Chemistry}, publisher={Royal Society of Chemistry (RSC)}, author={Soares, Ana R. M. and Taniguchi, Masahiko and Chandrashaker, Vanampally and Lindsey, Jonathan S.}, year={2013}, pages={1073} } @article{aravindu_kim_taniguchi_dilbeck_diers_bocian_holten_lindsey_2013, title={Synthesis and photophysical properties of chlorins bearing 0–4 distinct meso-substituents}, volume={12}, ISSN={1474-905X 1474-9092}, url={http://dx.doi.org/10.1039/C3PP50240F}, DOI={10.1039/C3PP50240F}, abstractNote={The presence of substituents at designated sites about the chlorin macrocycle can alter the spectral properties, a phenomenon that can be probed through synthesis. Prior syntheses have provided access to chlorins bearing distinct aryl substituents (individually or collectively) at the 5, 10, and 15-positions, but not the 20-position. A new Western half (5-phenyl-2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin) has been employed in condensation with an Eastern half (9-bromodipyrromethane-1-carboxaldehyde) followed by oxidative cyclization to give (5% yield) the zinc(ii) 20-phenylchlorin. Condensation of the same Western half and a diaryl-substituted Eastern half provided (11% yield) the zinc(ii) 5,10,20-triarylchlorin; demetalation with TFA followed by 15-bromination and Suzuki coupling gave the free base 5,10,15,20-tetraarylchlorin. Altogether, 10 new synthetic chlorins have been prepared. The near-UV (B) absorption band of the free base chlorins shifts bathochromically from 389 to 429 nm and that for the zinc chlorins from 398 to 420 nm as the number of meso -aryl rings is increased stepwise from 0-4. The long-wavelength (Q_y) absorption band undergoes a bathochromic and hypochromic shift upon increase in number of meso -aryl groups. Regardless of the number and positions of the meso -aryl substituents (including “walking a phenyl group around the ring”), the respective fluorescence quantum yields (0.17 to 0.27) and singlet excited-state lifetimes (9.4 to 13.1 ns) are comparable among the free base chlorins and the same is true for the zinc chelates (0.057 to 0.080; 1.2 to 1.6 ns). Density functional theory calculations show that of the frontier molecular orbitals of the chlorin, the energy of the HOMO−1 is the most affected by meso -aryl substituents, undergoing progressive destabilization as the number of meso -aryl groups is increased. The availability of chlorins with 0-4 distinct meso -aryl substituents provides the individual stepping-stones to bridge the known unsubstituted chlorin and the meso -tetraarylchlorins.}, number={12}, journal={Photochemical & Photobiological Sciences}, publisher={Royal Society of Chemistry (RSC)}, author={Aravindu, Kunche and Kim, Han-Je and Taniguchi, Masahiko and Dilbeck, Preston L. and Diers, James R. and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2013}, pages={2089} } @article{taniguchi_soares_chandrashaker_lindsey_2012, title={A tandem combinatorial model for the prebiogenesis of diverse tetrapyrrole macrocycles}, volume={36}, ISSN={1144-0546 1369-9261}, url={http://dx.doi.org/10.1039/c2nj21050a}, DOI={10.1039/c2nj21050a}, abstractNote={The extant biosynthesis of tetrapyrrole macrocycles has been considered a paradigm for the prebiotic formation of such molecules, yet only a few analogous non-enzymic reactions along the overall process have been demonstrated. In a prior study, the aqueous non-enzymic reaction of a dione and an aminoketone (δ-aminolevulinic acid) afforded uroporphyrinogen, Nature's last universal precursor to all extant tetrapyrroles. Here, in one flask the non-enzymic combinatorial reaction of two diones (substituents = acetic acid and methyl) and two aminoketones (substituents = propionic acid and ethyl) yields four pyrroles, which upon subsequent combinatorial reaction afford a distribution of porphyrinogens. A software program for virtual library generation predicts 538 porphyrinogens from this [2 × 2] reaction (owing to combinations and permutations) of which there are 25 sets of isomers based on condensed formulas of substituents. The collection spans the entire range of polarity enabled by the biosynthesis including uro- (number of carboxylic acids = 8), copro- (4), meso- (2), and etio-porphyrinogen (0). The first two are successive intermediates in the extant biosynthesis, the latter two resemble in polarity the advanced biosynthetic products protoporphyrin and chlorophyll. Upon consideration of substituent patterns, the porphyrins (obtained by oxidation of the porphyrinogens) can be grouped into one of four polarity categories (predicted percentage): hydrophilic (0.4%), uncertain (83.6%), amphiphilic (15.6%), and hydrophobic (0.4%). HPLC and mass spectrometry data are consistent with expectations to the limit of analytical capabilities. Thus, in terms of the polarity of the tetrapyrrole macrocycles formed, an all-at-once non-enzymic combinatorial process recapitulates features of the stepwise biosynthetic pathway.}, number={4}, journal={New Journal of Chemistry}, publisher={Royal Society of Chemistry (RSC)}, author={Taniguchi, Masahiko and Soares, Ana R. M. and Chandrashaker, Vanampally and Lindsey, Jonathan S.}, year={2012}, pages={1057} } @article{chandrashaker_taniguchi_ptaszek_lindsey_2012, title={Competing Knorr and Fischer-Fink pathways to pyrroles in neutral aqueous solution}, volume={68}, ISSN={["0040-4020"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863630235&partnerID=MN8TOARS}, DOI={10.1016/j.tet.2012.05.080}, abstractNote={Abstract A proposed chemical model for the prebiogenesis of tetrapyrrole macrocycles relies on the condensation of a 3-alkyl-substituted 2,4-diketone and an α-aminoketone to form a pyrrole equipped for subsequent self-condensation leading to porphyrinogens. The condensation of acyclic reactants can proceed via competing Knorr (desired) and Fischer–Fink (undesired) pathways. Here, the Knorr and Fischer–Fink pathways are quantitated using (1) analogues of those in the proposed prebiotic route wherein the resulting pyrroles are blocked from subsequent condensation, and (2) a set of internal standards for quantitation of crude reaction mixtures by 1H NMR spectroscopy following extraction into CS2. The reaction of 1-amino-2-butanone and 3-methyl-2,4-pentanedione at 60 °C in aqueous solution at pH 7 for 24 h afforded the Knorr pyrrole and Fischer–Fink pyrrole in yields of 48% and 7%, respectively. The reaction in hot aqueous acid (pH 4.6, reflux, 30 min) afforded the Knorr pyrrole in diminished yield (22%) relative to that of the Fischer–Fink pyrrole (11%). The Knorr pyrrole (4-ethyl-2,3-dimethylpyrrole) is evanescent whereas the Fischer–Fink pyrrole (2,3,4-trimethyl-5-propanoylpyrrole) is quite stable; hence, rapid analysis of the reaction mixture (vs workup and isolation) is essential for accurate analysis.}, number={34}, journal={TETRAHEDRON}, publisher={Elsevier BV}, author={Chandrashaker, Vanampally and Taniguchi, Masahiko and Ptaszek, Marcin and Lindsey, Jonathan S.}, year={2012}, month={Aug}, pages={6957–6967} } @article{taniguchi_lindsey_2012, title={Diversity, isomer composition, and design of combinatorial libraries of tetrapyrrole macrocycles}, volume={16}, ISSN={["1088-4246"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84860487739&partnerID=MN8TOARS}, DOI={10.1142/s1088424612004628}, abstractNote={ Combinatorial libraries of substituted tetrapyrrole macrocycles, which can now be prepared via a variety of approaches, typically are rich in isomers. Terminology for describing such isomers (due to distinct patterns of peripheral substituents) is delineated in several illustrative examples. A hierarchical relationship exists of molecular formula, condensed formula(s) of substituents, set(s) of pyrrole collocates (conveying each pair of β-pyrrolic substituents), and isomers of substituted tetrapyrrole macrocycles. Isomers with identical pyrrole collocate sets can arise owing to distinct positions or orientations of the (homo- or hetero-substituted) pyrrolic units in a macrocycle. Consideration of a handful of virtual combinatorial libraries illustrates tradeoffs of library size, chemical richness, and isomeric content. As one example, octa-derivatization of a tetrapyrrole scaffold with eight reactants A–H affords 2,099,728 members (99.7% isomers, 82,251 pyrrole collocate sets, and 6,435 condensed formulas) whereas the reversible self-condensation of four pyrroles that bear the same eight entities (AB, CD, EF, GH) affords 538 members (93.5% isomers, 35 pyrrole collocate sets, and 35 condensed formulas). Derivatization affords all combinations and permutations whereas self-condensation of substituted pyrroles carries collocational restrictions. Understanding such tradeoffs and the structural origin of isomerism are important aspects in the design of tetrapyrrole combinatorial libraries. }, number={1}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, publisher={World Scientific Pub Co Pte Lt}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2012}, month={Jan}, pages={1–13} } @article{taniguchi_lindsey_2012, title={Enumeration of Isomers of Substituted Tetrapyrrole Macrocycles: From Classical Problems in Biology to Modern Combinatorial Libraries}, DOI={10.1142/9789814397605_0009}, journal={Handbook of Porphyrin Science (Volume 23)}, publisher={World Scientific Publishing Company}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2012}, month={Jul}, pages={1–80} } @article{soares_taniguchi_chandrashaker_lindsey_2012, title={Primordial Oil Slick and the Formation of Hydrophobic Tetrapyrrole Macrocycles}, volume={12}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84868383598&partnerID=MN8TOARS}, DOI={10.1089/ast.2012.0857}, abstractNote={The functional end products of the extant biosynthesis of tetrapyrrole macrocycles in photosynthetic organisms are hydrophobic: chlorophylls and bacteriochlorophylls. A model for the possible prebiogenesis of hydrophobic analogues of nature's photosynthetic pigments was investigated by reaction of acyclic reactants in five media: aqueous solution (pH 7, 60°C, 24 h); aqueous solution containing 0.1 M decanoic acid (which forms a turbid suspension of vesicles); or aqueous solution accompanied by dodecane, mesitylene, or a five-component organic mixture (each of which forms a phase-separated organic layer). The organic mixture was composed of equimolar quantities of decanoic acid, dodecane, mesitylene, naphthalene, and pentyl acetate. The reaction of 1,5-dimethoxy-3-methylpentan-2,4-dione and 1-aminobutan-2-one to give etioporphyrinogens was enhanced in the presence of decanoic acid, affording (following chemical oxidation) etioporphyrins (tetraethyltetramethylporphyrins) in yields of 1.4-10.8% across the concentration range of 3.75-120 mM. The yield of etioporphyrins was greater in the presence of the five-component organic mixture (6.6% at 120 mM) versus that with dodecane or mesitylene (2.1% or 2.9%, respectively). The reaction in aqueous solution with no added oil-slick constituents resulted in phase separation-where the organic reactants themselves form an upper organic layer-and the yield of etioporphyrins was 0.5-2.6%. Analogous reactions leading to uroporphyrins (hydrophilic, eight carboxylic acids) or coproporphyrins (four carboxylic acids) were unaffected by the presence of decanoic acid or dodecane, and all yields were at most ∼2% or ∼8%, respectively. Taken together, the results indicate a facile means for the formation of highly hydrophobic constituents of potential value for prebiotic photosynthesis.}, number={11}, journal={Astrobiology}, publisher={Mary Ann Liebert Inc}, author={Soares, Ana R. M. and Taniguchi, Masahiko and Chandrashaker, Vanampally and Lindsey, Jonathan S.}, year={2012}, month={Nov}, pages={1055–1068} } @article{soares_taniguchi_chandrashaker_lindsey_2012, title={Self-organization of tetrapyrrole constituents to give a photoactive protocell}, volume={3}, ISSN={2041-6520 2041-6539}, url={http://dx.doi.org/10.1039/c2sc01120d}, DOI={10.1039/c2sc01120d}, abstractNote={A tandem combinatorial reaction of four acyclic, colorless compounds (two α-aminoketones and two diones; one polar and one nonpolar for each) in aqueous solution (30 mM each, 60 °C, pH 7, 24 h) containing lipid vesicles and with or without quinones and solar illumination affords a distribution of up to 538 porphyrins in 1.6–3.9% overall yield. The reactions leading to the porphyrins can occur in either or both the aqueous phase and the hydrophobic membrane of the vesicles. The porphyrins encompass a broad range of polarity and partition in the aqueous-lipid medium. Two fractions obtained by size-exclusion chromatography include porphyrins associated with the lipid vesicles and porphyrins in the aqueous phase. The porphyrins in both phases are photoactive as demonstrated by fluorescence quantum yield measurements (Φf ∼ 0.07–0.08) and by the Krasnovsky reaction (a photosynthetic-like process). The constituents of the Krasnovsky reaction employed here are methyl red, ascorbic acid, and 2,6-dichlorophenolindophenol. Illumination of the two porphyrin-containing samples (aqueous phase or vesicles) in the presence of the Krasnovsky constituents results in the reduction of methyl red and oxidation of ascorbic acid. Thus, the overall process transforms a colorless aqueous suspension via four stages (two combinatorial reactions, oxidation, physical partitioning) to photoactive porphyrins in distinct venues. The process may provide a model for the origin of pigments that enable proto-photosynthesis.}, number={6}, journal={Chemical Science}, publisher={Royal Society of Chemistry (RSC)}, author={Soares, Ana R. M. and Taniguchi, Masahiko and Chandrashaker, Vanampally and Lindsey, Jonathan S.}, year={2012}, pages={1963} } @article{chen_sun_fan_taniguchi_mcdowell_yang_diers_bocian_holten_lindsey_2012, title={Synthesis and Physicochemical Properties of Metallobacteriochlorins}, volume={51}, ISSN={["1520-510X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84865712494&partnerID=MN8TOARS}, DOI={10.1021/ic301262k}, abstractNote={Access to metallobacteriochlorins is essential for investigation of a wide variety of fundamental photochemical processes, yet relatively few synthetic metallobacteriochlorins have been prepared. Members of a set of synthetic bacteriochlorins bearing 0-4 carbonyl groups (1, 2, or 4 carboethoxy substituents, or an annulated imide moiety) were examined under two conditions: (i) standard conditions for zincation of porphyrins [Zn(OAc)(2)·2H(2)O in N,N-dimethylformamide (DMF) at 60-80 °C], and (ii) treatment in tetrahydrofuran (THF) with a strong base [e.g., NaH or lithium diisopropylamide (LDA)] followed by a metal reagent MX(n). Zincation of bacteriochlorins that bear 2-4 carbonyl groups proceeded under the former method whereas those with 0-2 carbonyl groups proceeded with NaH or LDA/THF followed by Zn(OTf)(2). The scope of metalation (via NaH or LDA in THF) is as follows: (a) for bacteriochlorins that bear two electron-releasing aryl groups, M = Cu, Zn, Pd, and InCl (but not Mg, Al, Ni, Sn, or Au); (b) for bacteriochlorins that bear two carboethoxy groups, M = Ni, Cu, Zn, Pd, Cd, InCl, and Sn (but not Mg, Al, or Au); and (c) a bacteriochlorin with four carboethoxy groups was metalated with Mg (other metals were not examined). Altogether, 15 metallobacteriochlorins were isolated and characterized. Single-crystal X-ray analysis of 8,8,18,18-tetramethylbacteriochlorin reveals the core geometry provided by the four nitrogen atoms is rectangular; the difference in length of the two sides is ∼0.08 Å. Electronic characteristics of (metal-free) bacteriochlorins were probed through electrochemical measurements along with density functional theory calculation of the energies of the frontier molecular orbitals. The photophysical properties (fluorescence yields, triplet yields, singlet and triplet excited-state lifetimes) of the zinc bacteriochlorins are generally similar to those of the metal-free analogues, and to those of the native chromophores bacteriochlorophyll a and bacteriopheophytin a. The availability of diverse metallobacteriochlorins should prove useful in a variety of fundamental photochemical studies and applications.}, number={17}, journal={INORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Chen, Chih-Yuan and Sun, Erjun and Fan, Dazhong and Taniguchi, Masahiko and McDowell, Brian E. and Yang, Eunkyung and Diers, James R. and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2012}, month={Sep}, pages={9443–9464} } @article{lindsey_thamyongkit_taniguchi_bocian_2011, title={Encoding isotopic watermarks in molecular electronic materials as an anti-counterfeiting strategy. Application to porphyrins for information storage}, volume={15}, ISSN={["1099-1409"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80051761959&partnerID=MN8TOARS}, DOI={10.1142/s1088424611003458}, abstractNote={An approach for information storage employs tetrapyrrole macrocycles as charge-storage elements attached to a (semi)conductor in hybrid chips. Anti-counterfeiting measures must cohere with the tiny amounts of such electroactive material and strict constraints on composition in chips; accordingly, the incorporation of typical anti-counterfeiting taggants or microcarriers is precluded. The provenance of the tetrapyrroles can be established through the use of isotopic substitution integral to the macrocycle. The isotopic substitution can be achieved by rational site-specific incorporation or by combinatorial procedures. The formation of a mixture of such macrocycles with various isotopic composition (isotopically unmodified, isotopologues, isotopomers) provides the molecular equivalent of an indelible printed watermark. Resonance Raman spectroscopic examination can reveal the watermark, but not the underlying molecular and isotopic composition; imaging mass spectrometry can reveal the presence of isotopologues but cannot discriminate among isotopomers. Hence, deciphering the code that encrypts the watermark in an attempt at forgery is expected to be prohibitive. A brief overview is provided of strategies for incorporating isotopes in meso-substituted tetrapyrrole macrocycles.}, number={7-8}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, publisher={World Scientific Pub Co Pte Lt}, author={Lindsey, Jonathan S. and Thamyongkit, Patchanita and Taniguchi, Masahiko and Bocian, David F.}, year={2011}, pages={505–516} } @article{yang_kirmaier_krayer_taniguchi_kim_diers_bocian_lindsey_holten_2011, title={Photophysical Properties and Electronic Structure of Stable, Tunable Synthetic Bacteriochlorins: Extending the Features of Native Photosynthetic Pigments}, volume={115}, ISSN={["1520-5207"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80052828697&partnerID=MN8TOARS}, DOI={10.1021/jp205258s}, abstractNote={Bacteriochlorins, which are tetrapyrrole macrocycles with two reduced pyrrole rings, are Nature's near-infrared (NIR) absorbers (700-900 nm). The strong absorption in the NIR region renders bacteriochlorins excellent candidates for a variety of applications including solar light harvesting, flow cytometry, molecular imaging, and photodynamic therapy. Natural bacteriochlorins are inherently unstable due to oxidative conversion to the chlorin (one reduced pyrrole ring) or the porphyrin. The natural pigments are also only modestly amenable to synthetic manipulation, owing to a nearly full complement of substituents on the macrocycle. Recently, a new synthetic methodology has afforded access to stable synthetic bacteriochlorins wherein a wide variety of substituents can be appended to the macrocycle at preselected locations. Herein, the spectroscopic and photophysical properties of 33 synthetic bacteriochlorins are investigated. The NIR absorption bands of the chromophores range from ∼700 to ∼820 nm; the lifetimes of the lowest excited singlet state range from ∼2 to ∼6 ns; the fluorescence quantum yields range from ∼0.05 to ∼0.25; and the yield of the lowest triplet excited state is ∼0.5. The spectroscopic/photophysical studies of the bacteriochlorins are accompanied by density functional theory (DFT) calculations that probe the characteristics of the frontier molecular orbitals. The DFT calculations indicate that the impact of substituents on the spectral properties of the molecules derives primarily from effects on the lowest unoccupied molecular orbital. Collectively, the studies show how the palette of synthetic bacteriochlorins extends the properties of the native photosynthetic pigments (bacteriochlorophylls). The studies have also elucidated design principles for tuning the spectral and photophysical characteristics as required for a wide variety of photochemical applications.}, number={37}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society (ACS)}, author={Yang, Eunkyung and Kirmaier, Christine and Krayer, Michael and Taniguchi, Masahiko and Kim, Han-Je and Diers, James R. and Bocian, David F. and Lindsey, Jonathan S. and Holten, Dewey}, year={2011}, month={Sep}, pages={10801–10816} } @article{taniguchi_du_lindsey_2011, title={Virtual Libraries of Tetrapyrrole Macrocycles. Combinatorics, Isomers, Product Distributions, and Data Mining}, volume={51}, ISSN={["1549-960X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80053326969&partnerID=MN8TOARS}, DOI={10.1021/ci200240e}, abstractNote={A software program (PorphyrinViLiGe) has been developed to enumerate the type and relative amounts of substituted tetrapyrrole macrocycles in a virtual library formed by one of four different classes of reactions. The classes include (1) 4-fold reaction of n disubstituted heterocycles (e.g., pyrroles or diiminoisoindolines) to form β-substituted porphyrins, β-substituted tetraazaporphyrins, or α- or β-substituted phthalocyanines; (2) combination of m aminoketones and n diones to form m × n pyrroles, which upon 4-fold reaction give β-substituted porphyrins; (3) derivatization of an 8-point tetrapyrrole scaffold with n reagents, and (4) 4-fold reaction of n aldehydes and pyrrole to form meso-substituted porphyrins. The program accommodates variable ratios of reactants, reversible or irreversible reaction (reaction classes 1 and 2), and degenerate modes of formation. Pólya's theorem (for enumeration of cyclic entities) has also been implemented and provides validation for reaction classes 3 and 4. The output includes the number and identity of distinct reaction-accessible substituent combinations, the number and identity of isomers thereof, and the theoretical mass spectrum. Provisions for data mining enable assessment of the number of products having a chosen pattern of substituents. Examples include derivatization of an octa-substituted phthalocyanine with eight reagents to afford a library of 2,099,728 members (yet only 6435 distinct substituent combinations) and reversible reaction of six distinct disubstituted pyrroles to afford 2649 members (yet only 126 distinct substituent combinations). In general, libraries of substituted tetrapyrrole macrocycles occupy a synthetically accessible region of chemical space that is rich in isomers (>99% or 95% for the two examples, respectively).}, number={9}, journal={JOURNAL OF CHEMICAL INFORMATION AND MODELING}, publisher={American Chemical Society (ACS)}, author={Taniguchi, Masahiko and Du, Hai and Lindsey, Jonathan S.}, year={2011}, month={Sep}, pages={2233–2247} } @article{lindsey_chandrashaker_taniguchi_ptaszek_2011, title={Abiotic formation of uroporphyrinogen and coproporphyrinogen from acyclic reactants}, volume={35}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78650436322&partnerID=MN8TOARS}, DOI={10.1039/c0nj00716a}, abstractNote={Tetrapyrrole macrocycles (e.g., porphyrins) have long been proposed as key ingredients in the emergence of life, yet plausible routes for forming their essential pyrrole precursor have previously not been identified. Here, the anaerobic reaction of δ-aminolevulinic acid (ALA, 5–240 mM) with 5-methoxy-3-(methoxyacetyl)levulinic acid (1-AcOH, 5–240 mM) in water (pH 5–7) at 25–85 °C for a few hours to a few days affords uroporphyrinogen, which upon chemical oxidation gives uroporphyrin in overall yield of up to 10%. The key intermediate is the α-methoxymethyl-substituted analogue of the pyrrole porphobilinogen (PBG). Reaction of ALA and the decarboxy analogue of 1-AcOH (1-Me) gave coproporphyrinogen (without its biosynthetic precursor uroporphyrinogen as an intermediate); oxidation gave the corresponding coproporphyrin in yields comparable to those for uroporphyrin. In each case a mixture of porphyrin isomers was obtained, consistent with reversible oligopyrromethane formation. The route investigated here differs from the universal extant biosynthetic pathway to tetrapyrrole macrocycles, where uroporphyrinogen (isomer III) – nature's last common precursor to corrins, heme, and chlorophylls – is derived from eight molecules of ALA (via four molecules of PBG). The demonstration of the spontaneous self-organization of eight acyclic molecules to form the porphyrinogen under simple conditions may open the door to the development of a chemical model for the prebiogenesis of tetrapyrrole macrocycles.}, number={1}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Lindsey, Jonathan S. and Chandrashaker, Vanampally and Taniguchi, Masahiko and Ptaszek, Marcin}, year={2011}, pages={65–75} } @article{jiao_taniguchi_lindsey_bocian_2010, title={Activation Energies for Oxidation of Porphyrin Monolayers Anchored to Au(111)}, volume={26}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77957909893&partnerID=MN8TOARS}, DOI={10.1021/la102802n}, abstractNote={The activation energy for the oxidation of porphyrin monolayers anchored to gold surfaces is determined via measurement of the temperature dependence of the electron-transfer rates. The activation energy (1) increases with increasing surface concentration of the porphyrin and (2) is significantly lower (8.1-17 versus 37-49 kJ mol(-1)) when smaller, more mobile counterions (Cl(-) versus PF(6)(-)) are used as the supporting electrolyte. Regardless, the lower activation energies do not result in radically different electron-transfer rates for the different types of counterions owing to compensating entropic effects.}, number={20}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Jiao, Jieying and Taniguchi, Masahiko and Lindsey, Jonathan S. and Bocian, David F.}, year={2010}, month={Oct}, pages={15718–15721} } @article{diers_taniguchi_holten_lindsey_bocian_2010, title={Probing the Rate of Hole Transfer in Oxidized Porphyrin Dyads Using Thallium Hyperfine Clocks}, volume={132}, ISSN={["0002-7863"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77956074080&partnerID=MN8TOARS}, DOI={10.1021/ja105082d}, abstractNote={Understanding hole/electron-transfer processes among interacting constituents of multicomponent molecular architectures is central to the fields of artificial photosynthesis and molecular electronics. One strategy for examining ground-state hole/electron transfer in oxidized tetrapyrrolic arrays entails analysis of the hyperfine interactions observed in the electron paramagnetic resonance (EPR) spectrum of the pi-cation radical. Herein, it is demonstrated that (203)Tl/(205)Tl hyperfine "clocks" are greatly superior to those provided by (1)H, (14)N, or (13)C owing to the fact that the (203)Tl/(205)Tl hyperfine couplings are much larger (15-25 G) than those of the (1)H, (14)N, or (13)C nuclei (1-6 G). The large (203)Tl/(205)Tl hyperfine interactions permit accurate simulations of the EPR spectra and the extraction of specific rates of hole/electron transfer. The (203)Tl/(205)Tl hyperfine clock strategy is applied to a series of seven porphyrin dyads. All of the dyads are joined at a meso position of the porphyrin macrocycle via linkers of a range of lengths and composition (diphenylethyne, diphenylbutadiyne, and (p-phenylene)(n), where n = 1-4); substituents such as mesityl at the nonlinking meso positions are employed to provide organic solubility. The hole/electron-transfer time constants are in the hundreds of picoseconds to sub-10 ns regime, depending on the specific porphyrin and/or linker. Density functional theory calculations on the constituents of the dyads are consistent with the view that the relative energies of the porphyrin versus linker highest occupied molecular orbitals strongly influence the hole/electron-transfer rates. Variable-temperature EPR studies further demonstrate that the hole/electron-transfer process is at best weakly activated (12-15 kJ mol(-1)) at room temperature and somewhat below. At lower temperatures, the process is essentially activationless. The weak activation is attributed to restricted torsional motions of the phenyl rings of the linker. Collectively, the studies provide the physical basis for the rational design of multicomponent architectures for efficient hole/electron transfer.}, number={34}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, publisher={American Chemical Society (ACS)}, author={Diers, James R. and Taniguchi, Masahiko and Holten, Dewey and Lindsey, Jonathan S. and Bocian, David F.}, year={2010}, month={Sep}, pages={12121–12132} } @article{nieves-bernier_diers_taniguchi_holten_bocian_lindsey_2010, title={Probing the Rate of Hole Transfer in Oxidized Synthetic Chlorin Dyads via Site-Specific C-13-Labeling}, volume={75}, ISSN={["1520-6904"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952494274&partnerID=MN8TOARS}, DOI={10.1021/jo100527h}, abstractNote={Understanding electronic communication among interacting constituents of multicomponent molecular architectures is important for rational design in diverse fields including artificial photosynthesis and molecular electronics. One strategy for examining ground-state hole/electron transfer in an oxidized tetrapyrrolic array relies on analysis of the hyperfine interactions observed in the EPR spectrum of the pi-cation radical. This strategy has been previously employed to probe the hole/electron-transfer process in oxidized multiporphyrin arrays of normal isotopic composition, wherein (1)H and (14)N serve as the hyperfine "clocks", and in arrays containing site-specific (13)C-labels, which serve as additional hyperfine clocks. Herein, the hyperfine-clock strategy is applied to dyads of dihydroporphyrins (chlorins). Chlorins are more closely related structurally to chlorophylls than are porphyrins. A de novo synthetic strategy has been employed to introduce a (13)C label at the 19-position of the chlorin macrocycle, which is a site of large electron/hole density and is accessible synthetically beginning with (13)C-nitromethane. The resulting singly (13)C-labeled chlorin was coupled with an unlabeled chlorin to give a dyad wherein a diphenylethyne linker spans the 10-positions of the two zinc chlorins. EPR studies of the monocations of both the natural abundance and (13)C-labeled zinc chlorin dyads and benchmark zinc chlorin monomers reveal that the time scale for hole/electron transfer is in the 4-7 ns range, which is 5-10-fold longer than that in analogous porphyrin arrays. The slower hole/electron transfer rate observed for the chlorin versus porphyrin dyads is attributed to the fact that the HOMO is a(1u)-like for the chlorins versus a(2u)-like for the porphyrins; the a(1u)-like orbital exhibits little (or no) electron/hole density at the site of linker attachment whereas the a(2u)-like orbital exhibits significant electron/hole density at this site. Collectively, the studies of the chlorin and porphyrin dyads provide insights into the structural features that influence the hole/electron-transfer process.}, number={10}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Nieves-Bernier, Elias J. and Diers, James R. and Taniguchi, Masahiko and Holten, Dewey and Bocian, David F. and Lindsey, Jonathan S.}, year={2010}, month={May}, pages={3193–3202} } @misc{lindsey_taniguchi_ra_mo_balasubramanian_2010, title={Refined routes to chlorin building blocks}, volume={7,678,900}, number={2010 Mar. 16}, author={Lindsey, J. S. and Taniguchi, M. and Ra, D. and Mo, G. and Balasubramanian, T.}, year={2010} } @article{mass_taniguchi_ptaszek_springer_faries_diers_bocian_holten_lindsey_2011, title={Structural characteristics that make chlorophylls green: interplay of hydrocarbon skeleton and substituents}, volume={35}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78650499742&partnerID=MN8TOARS}, DOI={10.1039/c0nj00652a}, abstractNote={Understanding the effects of substituents on natural photosynthetic pigments is essential for gaining a deep understanding of why such pigments were selected over the course of evolution for use in photosynthetic systems. This knowledge should provide for a more thoughtful design of artificial light-harvesting systems. The hydrocarbon skeleton of all chlorophylls is phorbine, which contains an annulated five-membered (isocyclic) ring in addition to the reduced pyrrole ring characteristic of chlorins. A phorbine and a 131-oxophorbine (which bears an oxo group in the isocyclic ring) were synthesized as benchmark molecules for fundamental spectral and photophysical studies. The phorbine and 131-oxophorbine macrocycles lack peripheral substituents other than a geminal dimethyl group in the reduced ring to stabilize the chlorin chromophore. The spectral properties and electronic structure of the zinc or free base 131-oxophorbine closely resemble those of the corresponding analogues of chlorophyll a. Accordingly, the fundamental electronic properties of chlorophylls are primarily a consequence of the 131-oxophorbine base macrocycle.}, number={1}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Mass, Olga and Taniguchi, Masahiko and Ptaszek, Marcin and Springer, Joseph W. and Faries, Kaitlyn M. and Diers, James R. and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2011}, pages={76–88} } @article{taniguchi_mass_boyle_tang_diers_bocian_holten_lindsey_2010, title={Structural studies of sparsely substituted synthetic chlorins and phorbines establish benchmarks for changes in the ligand core and framework of chlorophyll macrocycles}, volume={979}, ISSN={["1872-8014"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955427819&partnerID=MN8TOARS}, DOI={10.1016/j.molstruc.2010.05.035}, abstractNote={Understanding the changes in molecular structure of tetrapyrrole macrocycles upon derivatization of the organic framework is essential for diverse studies ranging from metal complexation to formation of supramolecular assemblies. New, sparsely substituted free base chlorin, 17-oxochlorin, phorbine and 131-oxophorbine macrocycles provide benchmarks for naturally occurring hydroporphyrins and have been examined here by X-ray crystallography, resonance Raman spectroscopy, and density functional theoretical (DFT) calculations. The macrocycles contain no substituents other than a geminal-dimethyl group attached to the reduced, pyrroline ring. The X-ray studies indicate that the benchmark compounds exhibit only slight distortion from planarity, which increases along the series porphine < chlorin < oxochlorin < phorbine < oxophorbine. The elongated CβCβ bond distance due to sp3 versus sp2 hybridization in the pyrroline ring (ring D) of the (oxo)chlorins and (oxo)phorbines (1.52–1.54 Å) versus that of porphine (1.35 Å) is accompanied by altered bond angles in ring D. Introduction of ring E (exocyclic ring) in a chlorin to give the phorbine or oxophorbine causes alteration of the bond angles at many sites in the framework of the macrocycle; for example, the bond angles of N3C14C15 in the (oxo)phorbine are widened by ∼11° compared to those of porphine or the analogous sparsely substituted chlorin. As a result, the shape of the macrocycle core changes along the series of porphine (nearly square), (oxo)chlorin (kite-shaped), and (oxo)phorbine (right-angled trapezoid), and the core size increases in the order porphine < phorbine ∼ oxophorbine < oxochlorin ∼ chlorin. Comparison of the bond distances and angles in ring E of the phorbine versus oxophorbine indicates that the shortening of the C13C131 bond owing to the presence of the oxo-group is quite small, only 0.024 Å; thus, the unsymmetrical structure of ring E does not appear to be due to conjugation with the C131O group but may be a characteristic feature of the (oxo)phorbine framework. The X-ray data further indicate that the lengths of the oxochlorin C17O and oxophorbine C131O groups are essentially identical, a result also predicted by DFT calculations. Regardless, the observed frequencies for the stretching vibrations of the C17O (1721 cm−1) and C131O (1701 cm−1) groups are different and suggest that conjugation of the latter group with the π-system of the macrocycle is greater than that of the former group. Collectively, the studies provide new insights into the individual factors that give rise to the overall structural characteristics of various macrocycles.}, number={1-3}, journal={JOURNAL OF MOLECULAR STRUCTURE}, publisher={Elsevier BV}, author={Taniguchi, Masahiko and Mass, Olga and Boyle, Paul D. and Tang, Qun and Diers, James R. and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2010}, month={Aug}, pages={27–45} } @article{taniguchi_lindsey_2010, title={Synthesis of oligo(p-phenylene)-linked dyads containing free base, zinc(II) or thallium(III) porphyrins for studies in artificial photosynthesis}, volume={66}, ISSN={["0040-4020"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955918878&partnerID=MN8TOARS}, DOI={10.1016/j.tet.2010.05.059}, abstractNote={A series of (p-phenylene)n-linked meso-mesityl-substituted porphyrin dyads (n=2–4) was prepared via Suzuki coupling of zinc(II) and free base porphyrin building blocks. The resulting zinc(II)/free base porphyrin dyads were demetalated. The series of free base porphyrin dimers (n=1–4), four other porphyrin dimers (with p-phenylene, diphenylethyne or diphenylbutadiyne linkers; and aryl or tridec-7-yl meso substituents), and several benchmark monomers were converted to the thallium(III)chloride complexes under mild conditions. The collection of eight Tl(III)Cl/Tl(III)Cl dimers is designed for studies of ground-state hole-transfer processes and comparison with the excited-state energy- and hole-transfer processes of the corresponding Zn(II)/free base dyads. Altogether, 18 new porphyrin arrays and benchmark monomers have been prepared.}, number={30}, journal={TETRAHEDRON}, publisher={Elsevier BV}, author={Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2010}, month={Jul}, pages={5549–5565} } @article{song_taniguchi_speckbacher_yu_bocian_lindsey_holten_2009, title={Excited-State Energy Flow in Phenylene-Linked Multiporphyrin Arrays}, volume={113}, ISSN={["1520-6106"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67649303381&partnerID=MN8TOARS}, DOI={10.1021/jp902183g}, abstractNote={The dynamics and pathways for excited-state energy transfer in three dyads and five triads composed of combinations of zinc, magnesium, and free base porphyrins (denoted Zn, Mg, Fb) connected by p-phenylene linkers have been investigated. The processes in the triads include energy transfer between adjacent nonequivalent porphyrins, between adjacent equivalent porphyrins, and between nonadjacent nonequivalent porphyrins using the intervening porphyrin as a superexchange mediator. In the case of the triad ZnZnFbPhi, excitation of the zinc porphyrin (to yield Zn) ultimately leads to production of the excited free base porphyrin (Fb) via the three processes with the derived rate constants as follows: (2.8 ps)(-1) for ZnZn Fb --> ZnZnFb, (4 ps)(-1) for Zn ZnFb left arrow over right arrow ZnZn Fb, and (14 ps)(-1) for Zn ZnFb --> ZnZnFb. These results and those obtained for the other four triads show that energy transfer between nonadjacent sites is significant and is only 5-7-fold slower than between adjacent sites. This same scaling was found previously for arrays joined via diphenylethyne linkers. Simulations of the energy-transfer properties of fictive dodecameric arrays based on the data reported herein show that nonadjacent transfer steps make a significant contribution to the observed performance of such larger molecular architectures. Collectively, these results indicate that energy transfer between nonadjacent sites has important implications for the design of multichromophore arrays for molecular-photonic and solar-energy applications.}, number={23}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society (ACS)}, author={Song, Hee-eun and Taniguchi, Masahiko and Speckbacher, Markus and Yu, Lianhe and Bocian, David F. and Lindsey, Jonathan S. and Holten, Dewey}, year={2009}, month={Jun}, pages={8011–8019} } @article{song_taniguchi_diers_kirmaier_bocian_lindsey_holten_2009, title={Linker Dependence of Energy and Hole Transfer in Neutral and Oxidized Multiporphyrin Arrays}, volume={113}, ISSN={["1520-6106"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-73349086237&partnerID=MN8TOARS}, DOI={10.1021/jp9072558}, abstractNote={The excited-state photodynamics of the neutral and one-electron-oxidized forms of five porphyrin dyads were studied in benzonitrile containing tetrabutylammonium hexafluorophosphate as the supporting electrolyte. Each dyad contains a zinc porphyrin (Zn) and a free base porphyrin (Fb) joined by a linear biphenylene (Phi(2)), terphenylene (Phi(3)), quaterphenylene (Phi(4)), diphenylbutadiyne (L), or phenylethyne (E) linker (ZnFbPhi(2), ZnFbPhi(3), ZnFbPhi(4), ZnFbL, ZnFbE). The findings along with recent results on the neutral and oxidized forms of ZnFb dyads containing a diphenylethyne or phenylene linker (ZnFbU, ZnFbPhi) and steric hindrance to porphyrin-linker internal rotation at one or both ends of a diarylethyne linker (ZnFbD, ZnFbP, ZnFbB) give insights into the effects of linker characteristics (length, orbital energies, orbital overlap with the porphyrins) on the rate constants for excited-state energy transfer, excited-state hole transfer, and ground-state hole transfer. Analysis of the results is aided by density functional theory molecular orbital calculations and Forster energy-transfer calculations. Although the rate constants for linker-mediated through-bond excited-state energy transfer can be modulated significantly using a number of molecular design criteria (e.g., linker characteristics, interplay between porphyrin orbital characteristics, and linker attachment site), ground-state hole transfer, which also occurs via a linker-mediated through-bond electron-exchange mechanism, is primarily affected by the free-energy driving force for the process as dictated by the redox characteristics of the interacting porphyrins. The insights gained from this study should aid in the design of next-generation multichromophore arrays for solar energy applications.}, number={52}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society (ACS)}, author={Song, Hee-eun and Taniguchi, Masahiko and Diers, James R. and Kirmaier, Christine and Bocian, David F. and Lindsey, Jonathan S. and Holten, Dewey}, year={2009}, month={Dec}, pages={16483–16493} } @misc{lindsey_taniguchi_balakumar_fan_2009, title={Methods and intermediates for the synthesis of porphyrins}, volume={7,582,751}, number={2009 Sep. 1}, author={Lindsey, J. S. and Taniguchi, M. and Balakumar, A. and Fan, D.}, year={2009} } @article{krayer_balasubramanian_ruzie_ptaszek_cramer_taniguchi_lindsey_2009, title={Refined syntheses of hydrodipyrrin precursors to chlorin and bacteriochlorin building blocks}, volume={13}, ISSN={["1099-1409"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70450189510&partnerID=MN8TOARS}, DOI={10.1142/S1088424609001406}, abstractNote={ Bromo-substituted hydrodipyrrins are valuable precursors to synthetic bromo-chlorins and bromo-bacteriochlorins, which in turn are versatile substrates for derivatization in pursuit of diverse molecular designs. 8-bromo-2,3-dihydro-1-(1,1-dimethoxymethyl)-3,3-dimethyldipyrrin (1) is a crucial precursor in the rational synthesis of the bacteriochlorin building block 3,13-dibromo-8,8,18,18-tetramethylbacteriochlorin ( H2BC-Br3Br13) . 8-bromo-2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin (2) is a crucial precursor in the rational synthesis of the analogous 3,13-disubstituted chlorin building block (e.g. H2C-Br3M10Br13 ). The routes to 1 and 2 share a common precursor, namely 4-bromo-2-(2-nitroethyl)-1-N-tosylpyrrole (6-Ts), which is derived from pyrrole-2-carboxaldehyde. The prior seven-step synthesis of 1 from pyrrole-2-carboxaldehyde has limited access to H2BC-Br3Br13 given the large excesses of materials, extensive reliance on column chromatography, and low overall yield (1.4%). Refined procedures for synthesis of the common precursor 6-Ts as well as 1 and 2 afford the advantages of (1) diminished consumption of solvents and reagents, (2) limited or no use of chlorinated solvents, (3) limited or no chromatography, and (4) improved yields of most steps. Streamlined procedures enable the final two or three transformations to be performed without purification of intermediates. The new procedures facilitate the expedient preparation of 1 and 2 at the multigram scale. }, number={10}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, publisher={World Scientific Pub Co Pte Lt}, author={Krayer, Michael and Balasubramanian, Thiagarajan and Ruzie, Christian and Ptaszek, Marcin and Cramer, David L. and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2009}, month={Oct}, pages={1098–1110} } @article{muthiah_lahaye_taniguchi_ptaszek_lindsey_2009, title={Regioselective Bromination Tactics in the de Novo Synthesis of Chlorophyll b Analogues}, volume={74}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-66449131206&partnerID=MN8TOARS}, DOI={10.1021/jo9002954}, abstractNote={The ability to introduce substituents at designated sites about the perimeter of the chlorin or 13(1)-oxophorbine macrocycle is essential for fundamental studies related to chlorophylls. A chlorin is a dihydroporphyrin, whereas a 13(1)-oxophorbine is a chlorin containing an annulated oxopentano ring spanning positions 13 and 15. 13(1)-Oxophorbines bearing auxochromes at the 7-position of the macrocycle are valuable targets given their resemblance to chlorophyll a or b, which contains the 13(1)-oxophorbine skeleton and bears a 7-methyl or 7-formyl group, respectively. A rational route to 7-substituted 13(1)-oxophorbines was developed that relies on a new method for regioselective bromination. Under neutral conditions, a 13-acetyl-10-mesitylchlorin (FbC-M(10)A(13)) undergoes bromination (with 1 molar equiv of NBS in THF) both in ring B (7-position) and at the 15-position (42% versus 28% isolated yield), thereby thwarting installation of the isocyclic ring (ring E, spanning the 13-15 positions). Under acidic conditions (10% TFA in CH(2)Cl(2)), ring B is deactivated, and bromination occurs preferentially at the 15-position (87% yield). The capability for preferential 15-bromination is essential to install the isocyclic ring, after which bromination can be directed to the 7-position of ring B (neutral conditions, 86% yield). The ability to suppress bromination in ring B (under acidic media) has been exploited in syntheses of sparsely substituted analogues of chlorophyll b. The analogues contain a 7-substituent (acetyl, formyl, or TIPS-ethynyl), a 10-mesityl group, and the 18,18-dimethyl group as the only substituents in the 13(1)-oxophorbine skeleton. The three analogues exhibit absorption spectral features that closely resemble those of free base analogues of chlorophyll b. Taken together, the facile access to chlorins and 13(1)-oxophorbines bearing substituents at distinct sites should enable fundamental spectroscopic studies and diverse applications.}, number={9}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Muthiah, Chinnasamy and Lahaye, Dorothee and Taniguchi, Masahiko and Ptaszek, Marcin and Lindsey, Jonathan S.}, year={2009}, month={May}, pages={3237–3247} } @article{lindsey_ptaszek_taniguchi_2009, title={Simple Formation of an Abiotic Porphyrinogen in Aqueous Solution}, volume={39}, ISSN={["1573-0875"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77949775456&partnerID=MN8TOARS}, DOI={10.1007/s11084-009-9168-3}, abstractNote={Porphyrins have long been proposed as key ingredients in the emergence of life yet plausible routes for forming their essential pyrrole precursor have heretofore not been identified. Here we show that the anaerobic reaction of δ-aminolevulinic acid (ALA, 1-5 mM) with the β-ketoester methyl 4-methoxyacetoacetate (2-40 mM) in water (pH5-7) at 70-100°C for >6 h affords the porphyrinogen, which upon chemical oxidation gives the corresponding porphyrin in overall yield of up to 10%. The key intermediate is the α-methoxymethyl-substituted pyrrole, which undergoes tetramerization and macrocycle formation under kinetic control. The resulting type-I porphyrin bears four propionic acid and four carbomethoxy groups, is distinct from porphyrins (e.g., uroporphyrin or coproporphyrin) derivable from ALA alone via the extant universal biosynthetic path to tetrapyrroles, and is photoactive upon assembly into cationic micelles in aqueous solution. The simple self-organization of eight acyclic molecules into a tetrapyrrole macrocycle, from which a porphyrin is derived that is photoactive in lipid assemblies, augurs well for the spontaneous origin of catalysts and pigments essential for prebiotic metabolism and proto-photosynthesis.}, number={6}, journal={ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES}, publisher={Springer Nature}, author={Lindsey, Jonathan S. and Ptaszek, Marcin and Taniguchi, Masahiko}, year={2009}, month={Dec}, pages={495–515} } @article{mass_ptaszek_taniguchi_diers_kee_bocian_holten_lindsey_2009, title={Synthesis and Photochemical Properties of 12-Substituted versus 13-Substituted Chlorins}, volume={74}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-68049111576&partnerID=MN8TOARS}, DOI={10.1021/jo900706x}, abstractNote={Understanding the effects of substituents on natural photosynthetic pigments is essential for the rational design of artificial photosynthetic systems. The long-wavelength absorption of chlorins derives from a transition that encompasses rings A and C, which includes the 2,3- and 12,13-positions, respectively. Chlorophylls bear a 3-vinyl group and a 13-keto group, as well as a full complement of substituents at the other beta-pyrrole sites. Prior studies of sparsely substituted synthetic chlorins to probe the effects of substituents yielded 3,13-substituted chlorins that contain a geminal dimethyl group in the pyrroline ring (for stability) and a mesityl group at the 10-position. Attempts to prepare analogous chlorins lacking the 10-mesityl substituent encountered unexpected difficulties during construction of the Eastern half precursor (8,9-dibromo-1-formyldipyrromethane) to the 13-bromochlorin. Direct bromination of 1-formyldipyrromethane with 2 mol equiv of NBS at -78 degrees C led to an isomeric mixture of the desired 8,9-dibromodipyrromethane (minor) and the unexpected 7,9-dibromodipyrromethane (major). Hence, a new rational route was developed for the synthesis of 8,9-dibromo-1-formyldipyrromethane that entailed (i) InCl(3)-catalyzed condensation of 4-bromo-2-(hydroxymethyl)pyrrole and pyrrole to give the 8-bromodipyrromethane, (ii) 1-formylation, and (iii) 9-bromination. Two new substituted chlorins carrying auxochromes at the 3- and 13-positions were synthesized. The photophysical and redox properties of the 13-substituted chlorins were compared with those of isomeric 12-substituted chlorins, synthesized previously via a 7,9-dibromo-1-formyldipyrromethane. Such studies (static absorption and fluorescence spectroscopy, time-resolved fluorescence spectroscopy, electrochemistry of the zinc chelates, and density functional theoretical calculations) reveal only very slight differences between the isomeric 12- and 13-substituted chlorins.}, number={15}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Mass, Olga and Ptaszek, Marcin and Taniguchi, Masahiko and Diers, James R. and Kee, Hooi Ling and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2009}, month={Aug}, pages={5276–5289} } @article{laha_muthiah_taniguchi_mcdowell_ptaszek_lindsey_2009, title={Synthetic Chlorins Bearing Auxochromes at the 3- and 13-Positions}, volume={74}, ISSN={0022-3263 1520-6904}, url={http://dx.doi.org/10.1021/jo9010602}, DOI={10.1021/jo9010602}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionSynthetic Chlorins Bearing Auxochromes at the 3- and 13-PositionsJoydev K. Laha, Chinnasamy Muthiah, Masahiko Taniguchi, Brian E. McDowell, Marcin Ptaszek, and Jonathan S. Lindsey*Cite this: J. Org. Chem. 2009, 74, 14, 5122Publication Date (Web):June 15, 2009Publication History Published online15 June 2009Published inissue 17 July 2009https://pubs.acs.org/doi/10.1021/jo9010602https://doi.org/10.1021/jo9010602correctionACS PublicationsCopyright © 2009 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views746Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (33 KB) Get e-AlertscloseSUBJECTS:Bromine,Chemical structure,Molecular structure,Photochemical properties,Regiochemistry Get e-Alerts}, number={14}, journal={The Journal of Organic Chemistry}, publisher={American Chemical Society (ACS)}, author={Laha, Joydev K. and Muthiah, Chinnasamy and Taniguchi, Masahiko and McDowell, Brian E. and Ptaszek, Marcin and Lindsey, Jonathan S.}, year={2009}, month={Jul}, pages={5122–5122} } @article{taniguchi_cramer_bhise_kee_bocian_holten_lindsey_2008, title={Accessing the near-infrared spectral region with stable, synthetic, wavelength-tunable bacteriochlorins}, volume={32}, ISSN={["1369-9261"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-45149130353&partnerID=MN8TOARS}, DOI={10.1039/b717803d}, abstractNote={The near-infrared (NIR) spectral region has been comparatively under-utilized for diverse materials and medical applications owing to the lack of chromophores that afford stability, solubility, synthetic malleability, and tunable photophysical features. Bacteriochlorins are attractive candidates in this regard; however, preparation via modification of naturally occurring bacteriochlorophylls or reduction of porphyrins or chlorins has proved cumbersome. To overcome such limitations, a dibromobacteriochlorin (BC-Br3Br13) was prepared de novo by the acid-catalyzed condensation of an 8-bromodihydrodipyrrin-acetal. BC-Br3Br13 bears (1) a geminal dimethyl group in each reduced ring to block adventitious dehydrogenation, and (2) bromo groups at the 3- and 13-positions for further chemical modifications. BC-Br3Br13 was subjected to four types of Pd-mediated coupling reaction (Suzuki, Stille, Sonogashira, dehalogenation) to give bacteriochlorins bearing substituents at the 3- and 13-positions (phenyl, vinyl, acetyl, phenylethynyl), and a benchmark bacteriochlorin lacking such substituents. The 3,13-divinylbacteriochlorin was transformed to the 3,13-diformylbacteriochlorin. Depending on the substituents at the 3- and 13-positions, the position of the long-wavelength absorption maximum (Qy(0,0) band) lies between 713 and 771 nm, the fluorescence emission maximum lies between 717 and 777 nm, and the fluorescence quantum yield ranges from 0.15 to 0.070. The ability to introduce a wide variety of functional groups via Pd-mediated coupling reactions and the tunable absorption and emission spectral properties suggest that synthetic bacteriochlorins are viable candidates for a wide variety of photochemical applications.}, number={6}, journal={NEW JOURNAL OF CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Taniguchi, Masahiko and Cramer, David L. and Bhise, Anil D. and Kee, Hooi Ling and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2008}, pages={947–958} } @article{jiao_schmidt_taniguchi_lindsey_bocian_2008, title={Comparison of Electron-Transfer Rates for Metal- versus Ring-Centered Redox Processes of Porphyrins in Monolayers on Au(111)}, volume={24}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55549087896&partnerID=MN8TOARS}, DOI={10.1021/la8019843}, abstractNote={The standard electron-transfer rate constants ( k ( 0 )) are measured for redox processes of Fe versus Zn porphyrins in monolayers on Au(111); the former undergoes a metal-centered redox process (conversion between Fe (III) and Fe (II) oxidation states) whereas the latter undergoes a ring-centered redox process (conversion between the neutral porphyrin and the pi-cation radical). Each porphyrin contains three meso-mesityl groups and a benzyl thiol for surface attachment. Under identical solvent (propylene carbonate)/electrolyte (1.0 M Bu 4NCl) conditions, the Zn (II) center has a coordinated Cl (-) ion when the porphyrin is in either the neutral or oxidized state. In the case of the Fe porphyrin, two species are observed a low-potential form ( E l (0) approximately -0.6 V) wherein the metal center has a coordinated Cl (-) ion when it is in either the Fe (II) or Fe (III) state and a high-potential form ( E h (0) approximately +0.2 V) wherein the metal center undergoes ligand exchange upon conversion from the Fe (III) to Fe (II) states. The k ( 0 ) values observed for all of the porphyrins depend on surface concentration, with higher concentrations resulting in slower rates, consistent with previous studies on porphyrin monolayers. The k ( 0 ) values for the ring-centered redox process (Zn chelate) are 10-40 times larger than those for the metal-centered process (Fe chelate); the k ( 0 ) values for the two forms of the Fe porphyrin differ by a factor of 2-4 (depending on surface concentration), the Cl (-) exchanging form generally exhibiting a faster rate. The faster rates for the ring- versus metal-centered redox process are attributed to the participating molecular orbitals and their proximity to the surface (given that the porphyrins are relatively upright on the surface): a pi molecular orbital that has significant electron density at the meso-carbon atoms (one of which is the site of attachment of the linker to the surface anchoring thiol) versus a d-orbital that is relatively well localized on the metal center.}, number={20}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Jiao, Jieying and Schmidt, Izabela and Taniguchi, Masahiko and Lindsey, Jonathan S. and Bocian, David F.}, year={2008}, month={Oct}, pages={12047–12053} } @article{song_kirmaier_taniguchi_diers_bocian_lindsey_holten_2008, title={Determination of Ground-State Hole-Transfer Rates Between Equivalent Sites in Oxidized Multiporphyrin Arrays Using Time-Resolved Optical Spectroscopy}, volume={130}, ISSN={["0002-7863"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-56449089593&partnerID=MN8TOARS}, DOI={10.1021/ja805673m}, abstractNote={Excited-state charge separation in molecular architectures has been widely explored, yet ground-state hole (or electron) transfer, particularly involving equivalent pigments, has been far less studied, and direct quantitation of the rate of transfer often has proved difficult. Prior studies of ground-state hole transfer between equivalent zinc porphyrins using electron paramagnetic resonance techniques give a lower limit of approximately (50 ns)(-1) on the rates. Related transient optical studies of hole transfer between inequivalent sites [zinc porphyrin (Zn) and free base porphyrin (Fb)] give an upper limit of approximately (20 ps)(-1). Thus, a substantial window remains for the unknown rates of ground-state hole transfer between equivalent sites. Herein, the ground-state hole-transfer processes are probed in a series of oxidized porphyrin triads (ZnZnFb) with the focus being on determination of the rates between the nominally equivalent sites (Zn/Zn). The strategy builds upon recent time-resolved optical studies of the photodynamics of dyads wherein a zinc porphyrin is electrochemically oxidized and the attached free base porphyrin is photoexcited. The resulting energy- and hole-transfer processes in the oxidized ZnFb dyads are typically complete within 100 ps of excitation. Such processes are also present in the triads and serve as a starting point for determining the rates of ground-state hole transfer between equivalent sites in the triads. The rate constant of the Zn/Zn hole transfer is found to be (0.8 ns)(-1) for diphenylethyne-linked zinc porphyrins and increases only slightly to (0.6 ns)(-1) when a shorter phenylene linker is utilized. The rate decreases slightly to (1.1 ns)(-1) when steric constraints are introduced in the diarylethyne linker. In general, the rate constants for ground-state Zn/Zn hole transfer in oxidized arrays are a factor of 40 slower than those for Zn/Fb transfer. Collectively, the findings should aid the design of next-generation molecular architectures for applications in solar-energy conversion.}, number={46}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, publisher={American Chemical Society (ACS)}, author={Song, Hee-eun and Kirmaier, Christine and Taniguchi, Masahiko and Diers, James R. and Bocian, David F. and Lindsey, Jonathan S. and Holten, Dewey}, year={2008}, month={Nov}, pages={15636–15648} } @article{song_taniguchi_kirmaier_bocian_lindsey_holten_2009, title={Probing Ground-state Hole Transfer Between Equivalent, Electrochemically Inaccessible States in Multiporphyrin Arrays Using Time-resolved Optical Spectroscopy}, volume={85}, ISSN={["1751-1097"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-65349190560&partnerID=MN8TOARS}, DOI={10.1111/j.1751-1097.2008.00471.x}, abstractNote={AbstractA new strategy is described and implemented for determining the rates of hole‐transfer between equivalent porphyrins in multiporphyrin architectures. The approach allows access to these rates between sites that are not the most easily oxidized components of the array. The specific architectures investigated with this new strategy are triads consisting of one zinc porphyrin (Zn) and two free base porphyrins (Fb). The triads employ a diphenylethyne linker (ZnFbFbU) and a phenylene linker (ZnFbFbΦ). The zinc porphyrin is selectively oxidized to produce Zn+FbFb, the free base porphyrins are excited to produce the excited‐state mixture Zn+Fb*Fb and Zn+FbFb*, and the subsequent dynamics are monitored by ultrafast absorption spectroscopy. The system evolves by a combination of energy‐ and hole‐transfer processes involving (adjacent and nonadjacent) zinc and free base porphyrin constituents that are complete within 100 ps of excitation; the rate constants of many of these processes are derived from prior studies of the oxidized forms of the benchmark dyads (ZnFbU and ZnFbΦ). One of the excited‐state decay channels produces the metastable state ZnFbFb+ that decays to a second metastable state ZnFb+Fb by the target hole‐transfer process, followed by rapid hole transfer to produce the Zn+FbFb thermodynamic ground state of the system. The rate constant for hole transfer between the free base porphyrins in the oxidized ZnFbFb triads is found to be (0.5 ns)−1 and (0.6 ns)−1 across phenylene and diphenylethyne linkers, respectively. These rate constants are comparable to those recently measured, using a related but distinct strategy, for ground‐state hole transfer between zinc porphyrins in oxidized ZnZnFb triads. The two complementary strategies provide unique approaches for probing hole transfer between equivalent sites in multiporphyrin arrays, with the choice of method being guided by the particular target process and the ease of synthesis of the necessary architectures.}, number={3}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, publisher={Wiley}, author={Song, Hee-eun and Taniguchi, Masahiko and Kirmaier, Christine and Bocian, David F. and Lindsey, Jonathan S. and Holten, Dewey}, year={2009}, pages={693–704} } @misc{lindsey_taniguchi_ra_mo_balasubramanian_2008, title={Refined routes to chlorin building blocks}, volume={7,470,785}, number={2008 Dec. 30}, author={Lindsey, J. S. and Taniguchi, M. and Ra, D. and Mo, G. and Balasubramanian, T.}, year={2008} } @article{kee_kirmaier_tang_diers_muthiah_taniguchi_laha_ptaszek_lindsey_bocian_et al._2007, title={Effects of substituents on synthetic analogs of chlorophylls. Part 1: Synthesis, vibrational properties and excited-state decay characteristics}, volume={83}, ISSN={["1751-1097"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34548711333&partnerID=MN8TOARS}, DOI={10.1111/j.1751-1097.2007.00150.x}, abstractNote={AbstractUnderstanding the effects of substituents on the spectra of chlorins is essential for a wide variety of applications. Recent developments in synthetic methodology have made possible systematic studies of the properties of the chlorin macrocycle as a function of diverse types and patterns of substituents. In this paper, the spectral, vibrational and excited‐state decay characteristics are examined for a set of synthetic chlorins. The chlorins bear substituents at the 5,10,15 (meso) positions or the 3,13 (β) positions (plus 10‐mesityl in a series of compounds) and include 24 zinc chlorins, 18 free base (Fb) analogs and one Fb or zinc oxophorbine. The oxophorbine contains the keto‐bearing isocyclic ring present in the natural photosynthetic pigments (e.g. chlorophyll a). The substituents cause no significant perturbation to the structure of the chlorin macrocycle, as evidenced by the vibrational properties investigated using resonance Raman spectroscopy. In contrast, the fluorescence properties are significantly altered due to the electronic effects of substituents. For example, the fluorescence wavelength maximum, quantum yield and lifetime for a zinc chlorin bearing 3,13‐diacetyl and 10‐mesityl groups (662 nm, 0.28, 6.0 ns) differ substantially from those of the parent unsubstituted chlorin (602 nm, 0.062, 1.7 ns). Each of these properties of the lowest singlet excited state can be progressively stepped between these two extremes by incorporating different substituents. These perturbations are associated with significant changes in the rate constants of the decay pathways of the lowest excited singlet state. In this regard, the zinc chlorins with the red‐most fluorescence also have the greatest radiative decay rate constant and are expected to have the fastest nonradiative internal conversion to the ground state. Nonetheless, these complexes have the longest singlet excited‐state lifetime. The Fb chlorins bearing the same substituents exhibit similar fluorescence properties. Such combinations of factors render the chlorins suitable for a range of applications that require tunable coverage of the solar spectrum, long‐lived excited states and red‐region fluorescence.}, number={5}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, author={Kee, Hooi Ling and Kirmaier, Christine and Tang, Quin and Diers, James R. and Muthiah, Chinnasamy and Taniguchi, Masahiko and Laha, Joydev K. and Ptaszek, Marcin and Lindsey, Jonathan S. and Bocian, David F. and et al.}, year={2007}, pages={1110–1124} } @article{kee_kirmaier_tang_diers_muthiah_taniguchi_laha_ptaszek_lindsey_bocian_et al._2007, title={Effects of substituents on synthetic analogs of chlorophylls. Part 2: Redox properties, optical spectra and electronic structure}, volume={83}, ISSN={["1751-1097"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34548759138&partnerID=MN8TOARS}, DOI={10.1111/j.1751-1097.2007.00151.x}, abstractNote={AbstractThe optical absorption spectra and redox properties are presented for 24 synthetic zinc chlorins and 18 free base analogs bearing a variety of 3,13 (β) and 5,10,15 (meso) substituents. Results are also given for a zinc and free base oxophorbine, which contain the keto‐bearing isocyclic ring present in the natural photosynthetic pigments such as chlorophyll a. Density functional theory calculations were carried out to probe the effects of the types and positions of substituents on the characteristics (energies, electron distributions) of the frontier molecular orbitals. A general finding is that the 3,13 positions are more sensitive to the effects of auxochromes than the 5,10,15 positions. The auxochromes investigated (acetyl > ethynyl > vinyl > aryl) cause a significant redshift and intensification of the Qy band upon placement at the 3,13 positions, whereas groups at the 5,10,15 positions result in much smaller redshifts that are accompanied by a decrease in relative Qy intensity. In addition, the substituent‐induced shifts in first oxidation and reduction potentials faithfully track the energies of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO), respectively. The calculations show that the LUMO is shifted more by substituents than the HOMO, which derives from the differences in the electron densities of the two orbitals at the substituent sites. The trends in the substituent‐induced effects on the wavelengths and relative intensities of the major features (By, Bx, Qx, Qy) in the near‐UV to near‐IR absorption bands are well accounted for using Gouterman’s four‐orbital model, which incorporates the effects of the substituents on the HOMO−1 and LUMO+1 in addition to the HOMO and LUMO. Collectively, the results and analysis presented herein and in the companion paper provide insights into the effects of substituents on the optical absorption, redox and other photophysical properties of the chlorins. These insights form a framework that underpins the rational design of chlorins for applications encompassing photomedicine and solar‐energy conversion.}, number={5}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, publisher={Wiley}, author={Kee, Hooi Ling and Kirmaier, Christine and Tang, Gun and Diers, James R. and Muthiah, Chinnasamy and Taniguchi, Masahiko and Laha, Joydev K. and Ptaszek, Marcin and Lindsey, Jonathan S. and Bocian, David F. and et al.}, year={2007}, pages={1125–1143} } @article{stromberg_marton_kee_kirmaier_diers_muthiah_taniguchi_lindsey_bocian_meyer_et al._2007, title={Examination of tethered porphyrin, chlorin, and bacteriochlorin molecules in mesoporous metal-oxide solar cells}, volume={111}, ISSN={["1932-7447"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35748969147&partnerID=MN8TOARS}, DOI={10.1021/jp0749928}, abstractNote={The performance of five tetrapyrrole molecules as sensitizers in regenerative solar cells was evaluated. The tetrapyrroles form two sets. One set contains three meso-substituted porphyrins that differ only in the nature of their surface-binding tether:  isophthalic acid, ethynylisophthalic acid, or cyanoacrylic acid. The other set includes the ethynylisophthalic acid tether attached to porphyrin, chlorin, and bacteriochlorin macrocycles, which contain zero, one, and two saturated pyrrole rings, respectively. Incident photon-to-current efficiency was measured for each sensitizer loaded onto a mesoporous TiO2 semitransparent electrode in a solar cell. The porphyrin bearing the cyanoacrylic acid tether gives the largest peak and integrated (350−900 nm) photocurrent density of the five tetrapyrrole molecules. For this sensitizer, a quasi-monochromatic power conversion efficiency of 21% was obtained at the Soret maximum (450 nm), along with a fill factor of 0.69. To elucidate the molecular origins of the effec...}, number={42}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, publisher={American Chemical Society (ACS)}, author={Stromberg, Jonathan R. and Marton, Andras and Kee, Hooi Ling and Kirmaier, Christine and Diers, James R. and Muthiah, Chinnasamy and Taniguchi, Masahiko and Lindsey, Jonathan S. and Bocian, David F. and Meyer, Gerald J. and et al.}, year={2007}, month={Oct}, pages={15464–15478} } @article{fan_taniguchi_lindsey_2007, title={Regioselective 15-bromination and functionalization of a stable synthetic bacteriochlorin}, volume={72}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34447323851&partnerID=MN8TOARS}, DOI={10.1021/jo070785s}, abstractNote={5-Methoxy-8,8,18,18-tetramethyl-2,12-di-p-tolylbacteriochlorin (MeO-BC) undergoes regioselective electrophilic bromination with NBS to give the 15-bromo analogue (MeO-BC-Br15) in 85% yield. By contrast, the bacteriochlorin lacking the 5-methoxy group (8,8,18,18-tetramethyl-2,12-di-p-tolylbacteriochlorin, H-BC) gives a mixture of two monobromo- and two dibromobacteriochlorins. Deuterium exchange of both bacteriochlorins (H-BC and MeO-BC) in acidic media (TFA-d) occurs preferentially at the beta-pyrrole positions (3, 13) > unhindered meso-positions (5, 15 for H-BC; 15 for MeO-BC) > hindered meso-positions (10, 20). The 15-bromo-5-methoxybacteriochlorin MeO-BC-Br15 was subjected to three types of Pd-mediated coupling reactions (Suzuki, Sonogashira, Hartwig-Buchwald) to give six bacteriochlorins bearing functional groups at the 15-position (49% to 85% yield). The groups include 4-(tert-butoxycarbonylmethoxy)phenyl, 4-pyridyl, 3,5-diformylphenyl, phenylethynyl, TIPS-ethynyl, and N-benzamido. The presence of the 15-ethynyl moiety shifts the position of the long-wavelength Qy band from 732 nm to approximately 753 nm. The ability to introduce a range of groups at a specific site enables synthetic bacteriochlorins to be tailored for a variety of applications.}, number={14}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Fan, Dazhong and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2007}, month={Jul}, pages={5350–5357} } @misc{ptaszek_mcdowell_taniguchi_kim_lindsey_2007, title={Sparsely substituted chlorins as core constructs in chlorophyll analogue chemistry. Part 1: Synthesis}, volume={63}, ISSN={["0040-4020"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33947635677&partnerID=MN8TOARS}, DOI={10.1016/j.tet.2007.02.038}, abstractNote={Five routes to stable chlorins bearing 0 or 1 meso substituents have been investigated, among which reaction of a 9-bromo-1-formyldipyrromethane and 2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin proved most effective. Application of this route afforded metallochlorins [Cu(II), Zn(II), Pd(II)] including the chlorin lacking any beta-pyrrole and meso substituents.}, number={18}, journal={TETRAHEDRON}, publisher={Elsevier BV}, author={Ptaszek, Marcin and McDowell, Brian E. and Taniguchi, Masahiko and Kim, Han-Je and Lindsey, Jonathan S.}, year={2007}, month={Apr}, pages={3826–3839} } @article{taniguchi_ptaszek_mcdowell_lindsey_2007, title={Sparsely substituted chlorins as core constructs in chlorophyll analogue chemistry. Part 2: Derivatization}, volume={63}, ISSN={["0040-4020"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33947700461&partnerID=MN8TOARS}, DOI={10.1016/j.tet.2007.02.076}, abstractNote={Stable chlorins bearing few or no substituents have been subjected to a variety of reactions including demetalation, magnesium insertion, oxochlorin formation, and bromination followed by Suzuki coupling. The kinetics of deuteration also have been determined for two oxochlorins and a series of chlorins bearing 0, 1, 2, or 3 meso-aryl substituents.}, number={18}, journal={TETRAHEDRON}, publisher={Elsevier BV}, author={Taniguchi, Masahiko and Ptaszek, Marcin and McDowell, Brian E. and Lindsey, Jonathan S.}, year={2007}, month={Apr}, pages={3840–3849} } @article{taniguchi_ptaszek_mcdowell_boyle_lindsey_2007, title={Sparsely substituted chlorins as core constructs in chlorophyll analogue chemistry. Part 3: Spectral and structural properties}, volume={63}, ISSN={["0040-4020"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33947694765&partnerID=MN8TOARS}, DOI={10.1016/j.tet.2007.02.040}, abstractNote={The availability of stable chlorins bearing few or no substituents has enabled a variety of fundamental studies. The studies described herein report absorption spectra of diverse chlorins, comparative NMR features of chlorins bearing 0-3 meso-aryl substituents, and X-ray structures of the fully unsubstituted chlorin and the oxochlorin.}, number={18}, journal={TETRAHEDRON}, publisher={Elsevier BV}, author={Taniguchi, Masahiko and Ptaszek, Marcin and McDowell, Brian E. and Boyle, Paul D. and Lindsey, Jonathan S.}, year={2007}, month={Apr}, pages={3850–3863} } @article{muthiah_taniguchi_kim_schmidt_kee_holten_bocian_lindsey_2007, title={Synthesis and photophysical characterization of porphyrin, chlorin and bacteriochlorin molecules bearing tethers for surface attachment}, volume={83}, ISSN={["0031-8655"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-36248978026&partnerID=MN8TOARS}, DOI={10.1111/j.1751-1097.2007.00195.x}, abstractNote={AbstractThe ability to tailor synthetic porphyrin, chlorin and bacteriochlorin molecules holds promise for diverse studies in artificial photosynthesis. Toward this goal, the synthesis and photophysical characterization of five tetrapyrrole compounds is described. Each compound bears a surface attachment group. One set contains three meso‐substituted porphyrins that differ only in the nature of a surface‐binding tether—isophthalic acid, ethynylisophthalic acid or cyanoacrylic acid. The other set includes a porphyrin, chlorin and bacteriochlorin each of which bears an ethynylisophthalic acid tether. The ester derivative of each compound was prepared for solution photophysical characterization studies. The photophysical studies include determination (in toluene or acetonitrile) of the electronic absorption and fluorescence spectra, fluorescence yield and lifetime of the lowest excited singlet state. The excited‐state lifetimes range from 1 to 5.6 ns for the five compounds. The radiative rate constant for the excited‐state decay was estimated from the photophysical data (fluorescence yield and excited‐state lifetime) and from Strickler–Berg analysis of the absorption and fluorescence spectra. The synthesis and characterization of the tetrapyrrole compounds underpin their use as sensitizers in molecular‐based solar cells.}, number={6}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, publisher={Wiley}, author={Muthiah, Chinnasamy and Taniguchi, Masahiko and Kim, Han-Je and Schmidt, Izabela and Kee, Hooi Ling and Holten, Dewey and Bocian, David F. and Lindsey, Jonathan S.}, year={2007}, pages={1513–1528} } @article{laha_muthiah_taniguchi_lindsey_2006, title={A new route for installing the isocyclic ring on chlorins yielding 13(1)-oxophorbines}, volume={71}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33750454076&partnerID=MN8TOARS}, DOI={10.1021/jo0608265}, abstractNote={A new route to 13(1)-oxophorbines, the parent macrocycle of chlorophylls, begins with the synthesis of a 13-bromochlorin. Pd-mediated coupling of the latter with tributyl(1-ethoxyvinyl)tin and subsequent acidic hydrolysis afforded the 13-acetylchlorin (1). Treatment of 1 with NBS afforded the 15-bromo analogue in 70% yield. Pd-mediated alpha-arylation closed the isocyclic ring to give the 13(1)-oxophorbine (2) in 85% yield. Facile access to 13(1)-oxophorbines should enable a variety of spectroscopic studies and diverse applications.}, number={18}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Laha, Joydev K. and Muthiah, Chinnasamy and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2006}, month={Sep}, pages={7049–7052} } @article{thamyongkit_bhise_taniguchi_lindsey_2006, title={Alkylthio unit as an alpha-pyrrole protecting group for use in dipyrromethane synthesis}, volume={71}, ISSN={["1520-6904"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-32144435067&partnerID=MN8TOARS}, DOI={10.1021/jo051806q}, abstractNote={The synthesis of porphyrin precursors requires the successive introduction of substituents at the pyrrole α- and α‘-positions (2- and 5-, respectively). An α-pyrrole substituent that serves as a temporary masking agent and is not deactivating would greatly facilitate such syntheses, particularly for β-(3,4)-unsubstituted pyrroles, but has heretofore not been available. A series of α-RS groups (R = Me, Et, n-decyl, Ph) have been investigated in this regard, including the determination of the kinetics of substitution at the pyrrolic 3-, 4-, and 5-positions and the application to dipyrromethane formation. The RS group was readily introduced into the pyrrole α-position by the reaction of 2-thiocyanatopyrrole (prepared from pyrrole, ammonium thiocyanate, and iodine) and the corresponding Grignard reagent RMgBr. Each 2-alkylthio group activated the pyrrole ring toward deuteration at the 3- or 5- (vs 4-) position. The dipyrromethane synthesis was carried out using a 2:1 ratio of 2-(RS)pyrrole/benzaldehyde with a...}, number={3}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Thamyongkit, P and Bhise, AD and Taniguchi, M and Lindsey, JS}, year={2006}, month={Feb}, pages={903–910} } @article{bhaumik_yao_borbas_taniguchi_lindsey_2006, title={Masked imidazolyl-dipyrromethanes in the synthesis of imidazole-substituted porphyrins}, volume={71}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33750879603&partnerID=MN8TOARS}, DOI={10.1021/jo061461r}, abstractNote={Imidazole-substituted metalloporphyrins are valuable for studies of self-assembly and for applications where water solubility is required. Rational syntheses of porphyrins bearing one or two imidazol-2-yl or imidazol-4-yl groups at the meso positions have been developed. The syntheses employ dipyrromethanes, 1-acyldipyrromethanes, and 1,9-diacyldipyrromethanes bearing an imidazole group at the 5-position. The polar, reactive imidazole unit was successfully masked by use of (1) the 2-(trimethylsilyl)ethoxymethyl (SEM) group at the imidazole pyrrolic nitrogen, and (2) a dialkylboron motif bound to the pyrrole of the dipyrromethane and coordinated to the imidazole imino nitrogen. The nonpolar nature of such doubly masked imidazolyl-dipyrromethanes facilitated handling. Selected masked dipyrromethanes were characterized by 11B and 15N NMR spectroscopy. Five distinct methods were examined to obtain trans-A2B2-, trans-AB2C-, and trans-AB-porphyrins. Each porphyrin contained one or two SEM-protected imidazole units. The SEM group could be removed with TBAF or HCl. Two zinc(II) porphyrins and a palladium(II) porphyrin bearing a single imidazole moiety were prepared and subjected to alkylation (with ethyl iodide, 1,3-propane sultone, or 1,4-butane sultone) to give water-soluble imidazolium- porphyrins. This work establishes the foundation for the rational synthesis of a variety of porphyrins containing imidazole units.}, number={23}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Bhaumik, Jayeeta and Yao, Zhen and Borbas, K. Eszter and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2006}, month={Nov}, pages={8807–8817} } @misc{lindsey_dhanalekshmi_laha_taniguchi_2006, title={Scalable synthesis of dipyrromethanes}, volume={7,022,862}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Lindsey, J. S. and Dhanalekshmi, S. and Laha, J. K. and Taniguchi, M.}, year={2006} } @article{laha_muthiah_taniguchi_mcdowell_ptaszek_lindsey_2006, title={Synthetic chlorins bearing auxochromes at the 3- and 13-positions}, volume={71}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33646926396&partnerID=MN8TOARS}, DOI={10.1021/jo060208o}, abstractNote={Synthetic chlorins bearing diverse auxochromes at the 3- and 13-positions of the macrocycle are valuable targets given their resemblance to chlorophylls a and b, which bear 3-vinyl and 13-keto groups. A de novo route has been exploited to construct nine zinc chlorins bearing substituents at the 3- and 13-positions and two benchmark zinc chlorins lacking such substituents. The chlorins are sterically uncongested and bear (1) a geminal dimethyl group in the reduced pyrroline ring, (2) a H, an acetyl, a triisopropylsilylethynyl (TIPS-ethynyl), or a vinyl at the 3-position, (3) a H, an acetyl, or TIPS-ethynyl at the 13-position, and (4) a H or a mesityl at the 10-position. The synthesis of the 13-substituted chlorins relied on p-TsOH x H2O-catalyzed condensation of an 8,9-dibromo-1-formyldipyrromethane (eastern half) and 2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin (western half), followed by metal-mediated oxidative cyclization, affording the 13-bromochlorin. Similar use of a bromo- or TIPS-ethynyl-substituted western half provided access to 3-substituted chlorins. A 3-bromo, 13-bromo, or 3,13-dibromochlorin was further transformed by Pd-coupling to introduce the vinyl group (via tributylvinyltin), TIPS-ethynyl group (via TIPS-acetylene), or acetyl group (via tributyl(1-ethoxyvinyl)tin, followed by acidic hydrolysis). In the 10-mesityl-substituted zinc chlorins, the series of substituents, 3-vinyl, 13-TIPS-ethynyl, 3-TIPS-ethynyl, 13-acetyl, 3,13-bis(TIPS-ethynyl), 3-TIPS-ethynyl-13-acetyl, or 3,13-diacetyl, progressively causes (1) a redshift in the absorption maximum of the B band (405-436 nm) and the Q(y) band (606-662 nm), (2) a relative increase in the intensity of the Q(y) band (I(B)/I(Q) = 4.2-1.5), and (3) an increase in the fluorescence quantum yield phi(f) (0.059-0.29). The zinc chlorins bearing a 3-TIPS-ethynyl-13-acetyl or a 3,13-diacetyl group exhibit a number of spectral properties resembling those of chlorophyll a or its zinc analogue. Taken together, this study provides access to finely tuned chlorins for spectroscopic studies and diverse applications.}, number={11}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Laha, Joydev K. and Muthiah, Chinnasamy and Taniguchi, Masahiko and McDowell, Brian E. and Ptaszek, Marcin and Lindsey, Jonathan S.}, year={2006}, month={May}, pages={4092–4102} } @article{fan_taniguchi_yao_dhanalekshmi_lindsey_2005, title={1,9-bis(N,N-dimethylaminomethyl)dipyrromethanes in the synthesis of porphyrins bearing one or two meso substituents}, volume={61}, ISSN={["0040-4020"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-25144489698&partnerID=MN8TOARS}, DOI={10.1016/j.tet.2005.08.028}, abstractNote={A synthesis of 5,15-disubstituted zinc-porphyrins has been developed that employs condensation of a 1,9-bis(N,N-dimethylaminomethyl)dipyrromethane+a dipyrromethane in refluxing ethanol containing zinc acetate followed by oxidation with DDQ. The N,N-dimethylaminomethylation of the dipyrromethane was achieved via Eschenmoser's reagent (N,N-dimethylmethyleneammonium iodide) in CH2Cl2 at room temperature. The synthesis is compatible with diverse substituents (e.g., alkyl, aryl, ester, acetal) and enables rapid synthesis of trans-AB-, A2-, and A-porphyrins. The synthesis of >40 zinc porphyrins has been surveyed; 13 zinc porphyrins were isolated in yields of 5–20% without detectable scrambling.}, number={43}, journal={TETRAHEDRON}, publisher={Elsevier BV}, author={Fan, DZ and Taniguchi, M and Yao, Z and Dhanalekshmi, S and Lindsey, JS}, year={2005}, month={Oct}, pages={10291–10302} } @article{taniguchi_balakumar_fan_mcdowell_lindsey_2005, title={Imine-substituted dipyrromethanes in the synthesis of porphyrins bearing one or two meso substituents}, volume={9}, ISSN={["1099-1409"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33244492173&partnerID=MN8TOARS}, DOI={10.1142/S1088424605000678}, abstractNote={ 5,15-substituted porphyrins are valuable compounds in bioorganic and materials chemistry. A new synthesis has been developed that employs 1,9-diformylation of a dipyrromethane, conversion of the diformyldipyrromethane to the bis(imino) derivative, and reaction of the bis(imino)dipyrromethane + a dipyrromethane to give the zinc-porphyrin bearing trans-AB-substituents. 1,9-diformylation was achieved via Vilsmeier reaction. Imination was achieved by treatment of the 1,9-diformyldipyrromethane with excess amine under neat conditions at room temperature. The porphyrin-forming reaction was carried out over 2 h in refluxing ethanol containing zinc acetate exposed to air. Oxidation of the intermediate porphyrinogen occurs aerobically. A complex composed of two bis(imino)dipyrromethanes and two zinc atoms was observed to form reversibly during the course of the reaction. A set of zinc-porphyrins with trans-AB-, A 2-, or A-substituents has been prepared in yields of ~30% (without detectable scrambling) with straightforward purification. The reaction is applicable to A/B substituent combinations of aryl/aryl, aryl/alkyl, and aryl/H. }, number={8}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, publisher={World Scientific Pub Co Pte Lt}, author={Taniguchi, M and Balakumar, A and Fan, DZ and McDowell, BE and Lindsey, JS}, year={2005}, pages={554–574} } @article{dixon_taniguchi_lindsey_2005, title={PhotochemCAD 2: A Refined Program with Accompanying Spectral Databases for Photochemical Calculations}, volume={81}, ISSN={["1751-1097"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-14744278395&partnerID=MN8TOARS}, DOI={10.1562/2004-11-06-TSN-361.1}, abstractNote={Abstract The PhotochemCAD program has been revised extensively. Calculations can be performed using eight modules (oscillator strength, transition dipole moment and natural radiative lifetime, Förster energy transfer, multicomponent analysis, blackbody radiator, artificial spectrum creation, transmission calculation, and analysis of energy transfer among linear multichromophore arrays). The user interface has been streamlined to facilitate visual display, operation of the various modules, input of user data via a wizard and output of spectra and calculations. The database of absorption and fluorescence spectra has been expanded to 150 photochemically relevant compounds. A database of solar spectra has been added. The program runs under Windows and is equipped with extensive literature references and help features, including a tutorial section with video files.}, number={1}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, publisher={Wiley}, author={Dixon, JM and Taniguchi, M and Lindsey, JS}, year={2005}, pages={212–213} } @article{dixon_taniguchi_lindsey_2007, title={PhotochemCAD 2: A Refined Program with Accompanying Spectral Databases for Photochemical Calculations¶}, volume={81}, DOI={10.1111/j.1751-1097.2005.tb01544.x}, abstractNote={ABSTRACTThe PhotochemCAD program has been revised extensively. Calculations can be performed using eight modules (oscillator strength, transition dipole moment and natural radiative lifetime, Förster energy transfer, multicomponent analysis, blackbody radiator, artificial spectrum creation, transmission calculation, and analysis of energy transfer among linear multichromophore arrays). The user interface has been streamlined to facilitate visual display, operation of the various modules, input of user data via a wizard and output of spectra and calculations. The database of absorption and fluorescence spectra has been expanded to 150 photochemically relevant compounds. A database of solar spectra has been added. The program runs under Windows and is equipped with extensive literature references and help features, including a tutorial section with video files.}, number={1}, journal={Photochemistry and Photobiology}, publisher={Wiley}, author={Dixon, James M. and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2007}, month={May}, pages={212–213} } @misc{lindsey_taniguchi_ra_m_balasubramanian_2005, title={Refined routes to chlorin building blocks}, volume={6,946,552}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Lindsey, J. S. and Taniguchi, M. and Ra, D. and M, G. and Balasubramanian, T.}, year={2005} } @article{ptaszek_bhaumik_kim_taniguchi_lindsey_2005, title={Refined synthesis of 2,3,4,5-tetrahydro-1,3,3-trimethyidipyrrin, a deceptively simple precursor to hydroporphyrins}, volume={9}, ISSN={["1520-586X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-26444474619&partnerID=MN8TOARS}, DOI={10.1021/op050087e}, abstractNote={2,3,4,5-Tetrahydro-1,3,3-trimethyldipyrrin (1) is a crucial building block in the rational synthesis of chlorins and oxochlorins. The prior 5-step synthesis of 1 from pyrrole-2-carboxaldehyde (2) employed relatively simple and well-known reactions yet suffered from several drawbacks, including limited scale (>/= 0.5 g of 1 per run). A streamlined preparation of 1 has been developed that entails four steps: (i) nitro-aldol condensation of 2 and nitromethane under neat conditions to give 2-(2-nitrovinyl)pyrrole (3), (ii) reduction of 3 with NaBH(4) to give 2-(2-nitroethyl)pyrrole (4), (iii) Michael addition of 4 with mesityl oxide under neat conditions or at high concentration to give gamma-nitrohexanonepyrrole 5, and (iv) reductive cyclization of 5 with zinc/ammonium formate to give 1. Several multistep transformations have been established, including the direct conversion of 2 --> 1. The advantages of the new procedures include (1) fewer steps, (2) avoidance of several problematic reagents, (3) diminished consumption of solvents and reagents, (4) lessened reliance on chromatography, and (5) scalability. The new procedures facilitate the preparation of 1 at the multigram scale.}, number={5}, journal={ORGANIC PROCESS RESEARCH & DEVELOPMENT}, publisher={American Chemical Society (ACS)}, author={Ptaszek, M and Bhaumik, J and Kim, HJ and Taniguchi, M and Lindsey, JS}, year={2005}, pages={651–659} } @article{tamaru_yu_youngblood_muthukumaran_taniguchi_lindsey_2004, title={A tin-complexation strategy for use with diverse acylation methods in the preparation of 1,9-diacyldipyrromethanes}, volume={69}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0842285782&partnerID=MN8TOARS}, DOI={10.1021/jo035622s}, abstractNote={The acylation of dipyrromethanes to form 1,9-diacyldipyrromethanes is an essential step in the rational synthesis of porphyrins. Although several methods for acylation are available, purification is difficult because 1,9-diacyldipyrromethanes typically streak extensively upon chromatography and give amorphous powders upon attempted crystallization. A solution to this problem has been achieved by reacting the 1,9-diacyldipyrromethane with Bu(2)SnCl(2) to give the corresponding dibutyl(5,10-dihydrodipyrrinato)tin(IV) complex. The reaction is selective for dipyrromethanes that bear acyl groups at both the 1- and 9-positions but otherwise is quite tolerant of diverse substituents. The diacyldipyrromethane-tin complexes are stable to air and water, are highly soluble in common organic solvents, crystallize readily, and chromatograph without streaking. Four methods (Friedel-Crafts, Grignard, Vilsmeier, benzoxathiolium salt) were examined for the direct 1,9-diacylation of a dipyrromethane or the 9-acylation of a 1-acyldipyrromethane. In each case, treatment of the crude reaction mixture with Bu(2)SnCl(2) and TEA at room temperature enabled facile isolation of multigram quantities of the 1,9-diacyldipyrromethane-tin complex. The diacyldipyrromethane-tin complexes could be decomplexed with TFA in nearly quantitative yield. Alternatively, use of a diacyldipyrromethane-tin complex in a porphyrin-forming reaction (reduction with NaBH(4), acid-catalyzed condensation with a dipyrromethane, DDQ oxidation) afforded the desired free base porphyrin in yield comparable to that obtained from the uncomplexed diacyldipyrromethane. The acylation/tin-complexation strategy has been applied to a bis(dipyrromethane) and a porphyrin-dipyrromethane. In summary, the tin-complexation strategy has broad scope, is compatible with diverse acylation methods, and greatly facilitates access to 1,9-diacyldipyrromethanes.}, number={3}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Tamaru, S and Yu, LH and Youngblood, WJ and Muthukumaran, K and Taniguchi, M and Lindsey, JS}, year={2004}, month={Feb}, pages={765–777} } @article{taniguchi_kim_ra_lindsey_2005, title={Introduction of a third meso substituent into 5,10-diaryl chlorins and oxochlorins}, volume={70}, ISSN={["1520-6904"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-11844252011&partnerID=MN8TOARS}, DOI={10.1021/jo048440m}, abstractNote={Chlorins/oxochlorins bearing distinct patterns of substituents are valuable compounds in bioorganic and materials chemistry. Treatment of a 5,10-diaryl-substituted chlorin or oxochlorin with TFA-d(1) resulted in selective deuteriation of the remaining meso positions (15, 20) rather than any of the beta-pyrrolic positions. Electrophilic iodination or bromination of a 5,10-diaryl-substituted chlorin proceeded with high regioselectivity, affording the 5,10-diaryl-15-halo-substituted chlorin. Iodination or bromination of a free base 5,10-diaryloxochlorin gave a mixture of products arising through halogenation at the 15-, 20-, and beta-pyrrolic positions, while bromination of a zinc 5,10-diaryloxochlorin selectively gave the 5,10-diaryl-20-bromo-substituted oxochlorin. The Suzuki coupling reaction of a phenyl boronic acid derivative and a 5,10-diaryl-15-iodooxochlorin or 5,10-diaryl-20-bromooxochlorin gave the corresponding 5,10,15- or 5,10,20-triaryloxochlorin. The introduction of a third aryl substituent into the chlorin or oxochlorin causes an approximately 5-nm red shift of the long wavelength Q(y) absorption band. Two phenylethyne-linked oxochlorin-oxochlorin dyads in distinct metalation states (zinc/free base, free base/zinc) were prepared by Sonogashira coupling reactions of a 5,10-diaryl-20-bromooxochlorin and a 10-substituted ethynylphenyl oxochlorin. This study provides access to new chlorins/oxochlorins that can be utilized in diverse applications.}, number={1}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Taniguchi, M and Kim, MN and Ra, D and Lindsey, JS}, year={2005}, month={Jan}, pages={275–285} } @article{dixon_taniguchi_lindsey_2004, title={PhotochemCAD 2. A Refined Program with Accompanying Spectral Database for Photochemical Calculations}, DOI={10.1562/2004-11-06-tsn-361}, abstractNote={The PhotochemCAD program has been revised extensively. Calculations can be performed using eight modules (oscillator strength, transition dipole moment and natural radiative lifetime, Forster energy transfer, multicomponent analysis, blackbody radiator, artificial spectrum creation, transmission calculation, and analysis of energy transfer among linear multichromophore arrays). The user interface has been streamlined to facilitate visual display, operation of the various modules, input of user data via a wizard and output of spectra and calculations. The database of absorption and fluorescence spectra has been expanded to 150 photochemically relevant compounds. A database of solar spectra has been added. The program runs under Windows and is equipped with extensive literature references and help features, including a tutorial section with video files.}, journal={Photochemistry and Photobiology}, publisher={Wiley}, author={Dixon, James M. and Taniguchi, Masahiko and Lindsey, Jonathan S.}, year={2004} } @article{hindin_kirmaier_diers_tomizaki_taniguchi_lindsey_bocian_holten_2004, title={Photophysical properties of phenylethyne-linked porphyrin and oxochlorin dyads}, volume={108}, ISSN={["1520-6106"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-3042636305&partnerID=MN8TOARS}, DOI={10.1021/jp037614l}, abstractNote={A set of porphyrin-porphyrin and oxochlorin-oxochlorin dyads has been prepared in which the constituent pigments are joined at the meso-positions by a phenylethyne linker. Attachment of an ethynyl substituent to the meso-position of a tetrapyrrolic macrocycle strongly perturbs the electronic properties of the ring. The inherent asymmetry of the phenylethyne linker affords the possibility of perturbing either end of the dyad. The porphyrin dyads include bis-Zn, Zn-free base (Fb), and bis-Zn species wherein 0, 1, or 2 of the three nonlinking aryl rings of one of the Zn porphyrins are perfluorinated. The two oxochlorin dyads are both ZnFb species in which the meso-ethyne substituent is located on either the Zn complex or the Fb. The dyads have been studied using static and time-resolved absorption and emission spectroscopy and electrochemical techniques. The optical and electrochemical properties of a series of monomeric reference compounds were also examined. The time-resolved optical studies reveal that energy transfer in the phenylethyne-linked dyads is faster by ∼10-fold or more than in analogous dyads joined by a diphenylethyne linker. In particular, energy transfer occurs with a rate constant of > (20 ps) - 1 between the phenylethyne-linked oxochlorins and an efficiency of >98%, to be compared with a rate of (140 ps) - 1 and an efficiency of 83% found previously for diphenylethyne-linked oxochlorins. Taken together, these results should be useful in the design of multipigment architectures that absorb in the red and undergo fast and efficient energy transfer, as required for light-harvesting applications.}, number={24}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society (ACS)}, author={Hindin, E and Kirmaier, C and Diers, JR and Tomizaki, KY and Taniguchi, M and Lindsey, JS and Bocian, DF and Holten, D}, year={2004}, month={Jun}, pages={8190–8200} } @misc{lindsey_taniguchi_prathapan_kim_kim_2004, title={Regioisomerically pure oxochlorins and methods of synthesis}, volume={6,765,092}, number={2004 July 20}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Lindsey, J. S. and Taniguchi, M. and Prathapan, S. and Kim, M. N. and Kim, H.-J.}, year={2004} } @article{tomizaki_lysenko_taniguchi_lindsey_2004, title={Synthesis of phenylethyne-linked porphyrin dyads}, volume={60}, ISSN={["0040-4020"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1042275557&partnerID=MN8TOARS}, DOI={10.1016/j.tet.2004.01.003}, abstractNote={Four new porphyrin dyads have been prepared for studies in artificial photosynthesis. The two porphyrins are joined at the meso positions via a phenylethyne linker and are present in zinc/zinc or zinc/free base metalation states. The porphyrin bearing the ethynyl unit incorporates zero, one, or two pentafluorophenyl groups at non-linking meso positions for tuning the porphyrin redox potentials. The synthetic approach entailed Pd-mediated coupling of porphyrin building blocks that bear a single ethynylphenyl or bromo/iodo substituent.}, number={9}, journal={TETRAHEDRON}, publisher={Elsevier BV}, author={Tomizaki, K and Lysenko, AB and Taniguchi, M and Lindsey, JS}, year={2004}, month={Feb}, pages={2011–2023} } @article{laha_dhanalekshmi_taniguchi_ambroise_lindsey_2003, title={A scalable synthesis of meso-substituted dipyrromethanes}, volume={7}, ISSN={["1520-586X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0346735296&partnerID=MN8TOARS}, DOI={10.1021/op034083q}, abstractNote={A one-flask synthesis of meso-substituted dipyrromethanes has been refined. The procedure entails reaction of an aldehyde in 100 equiv of pyrrole as the solvent containing a mild Lewis acid (e.g., InCl3) at room temperature. Following removal and recovery of excess pyrrole, the dipyrromethane is obtained by crystallization. The procedure generates minimal waste and does not require aqueous/organic extraction, chromatography, or distillation. The procedure has been scaled linearly to obtain >100 g of 5-phenyldipyrromethane. The utility of various analytical methods for characterizing dipyrromethanes has been investigated.}, number={6}, journal={ORGANIC PROCESS RESEARCH & DEVELOPMENT}, publisher={American Chemical Society (ACS)}, author={Laha, JK and Dhanalekshmi, S and Taniguchi, M and Ambroise, A and Lindsey, JS}, year={2003}, pages={799–812} } @article{taniguchi_ra_kirmaier_hindin_schwartz_diers_knox_bocian_lindsey_holten_2003, title={Comparison of excited-state energy transfer in arrays of hydroporphyrins (chlorins, oxochlorins) versus porphyrins: Rates, mechanisms, and design criteria}, volume={125}, ISSN={["0002-7863"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0242330789&partnerID=MN8TOARS}, DOI={10.1021/ja035987u}, abstractNote={A set of chlorin-chlorin and oxochlorin-oxochlorin dyads has been prepared with components in the same or different metalation states. In each case a 4,4'-diphenylethyne linker spans the respective 10-position of each macrocycle. The dyads have been studied using static and time-resolved absorption and emission spectroscopy, resonance Raman spectroscopy, and electrochemical techniques. Excited-state energy transfer from a zinc chlorin to a free-base (Fb) chlorin occurs with a rate constant of (110 ps)(-1) and an efficiency of 93%; similar values of (140 ps)(-1) and 83% are found for the corresponding oxochlorin dyad. Energy transfer in both dyads is slower and less efficient than found previously for the analogous porphyrin dyad, which displays a rate of (24 ps)(-1) and a yield of 99%. The slower rates and diminished efficiencies in the ZnFb chlorin and oxochlorin dyads versus the ZnFb porphyrin dyad are attributed to substantially weaker linker-mediated through-bond (TB) electron-exchange coupling (as indicated by resonance Raman data). Although the through-space (TS, i.e., dipole-dipole) coupling in the ZnFb-chlorin and -oxochlorin dyads is enhanced relative to the ZnFb porphyrin dyad (as indicated by Förster calculations), this enhancement is insufficient to compensate for the greatly diminished TB coupling. Taken together, the chlorin and oxochlorin dyads examined herein serve as benchmarks for elucidating the energy-transfer, electrochemical, and other properties of light-harvesting arrays containing multiple chlorins or oxochlorins.}, number={44}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Taniguchi, M and Ra, D and Kirmaier, C and Hindin, E and Schwartz, JK and Diers, JR and Knox, RS and Bocian, DF and Lindsey, JS and Holten, D}, year={2003}, month={Nov}, pages={13461–13470} } @article{kirmaier_hindin_schwartz_sazanovich_diers_muthukumaran_taniguchi_bocian_lindsey_holten_2003, title={Synthesis and excited-state photodynamics of perylene-bis(imide)-oxochlorin dyads. A charge-separation motif}, volume={107}, ISSN={["1520-6106"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037452013&partnerID=MN8TOARS}, DOI={10.1021/jp0269423}, abstractNote={Three perylene-oxochlorin dyads have been prepared and characterized with the goal of identifying charge-injection or molecular-switching motifs for use in molecular photonics. Each dyad consists of a perylene-bis(imide) dye (PDI) joined at the 10-position of a magnesium, zinc, or free base (Fb) oxochlorin via a diphenylethyne linker. Each dyad has been studied in both polar and nonpolar media using static and time-resolved optical spectroscopy and electrochemical techniques. Dyad PDI−MgO is an excellent charge-separation unit in which the excited perylene (∼3.5 ps lifetime) or the excited oxochlorin (lifetimes of 0.5 ns in benzonitrile and 1.0 ns in toluene) give rise to state PDI- MgO+ in high overall yield (>90%); the charge-separated state has a lifetime of ≥1 ns in both toluene and benzonitrile. The pathway for generating PDI- MgO+ from the excited perylene (PDI*) involves both hole transfer and energy transfer to the oxochlorin followed by electron transfer from the resulting MgO* to PDI. Similar de...}, number={15}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society (ACS)}, author={Kirmaier, C and Hindin, E and Schwartz, JK and Sazanovich, IV and Diers, JR and Muthukumaran, K and Taniguchi, M and Bocian, DF and Lindsey, JS and Holten, D}, year={2003}, month={Apr}, pages={3443–3454} } @article{taniguchi_kim_ra_schwartz_kirmaier_hindin_diers_prathapan_bocian_holten_et al._2002, title={Synthesis and electronic properties of regioisomerically pure oxochlorins}, volume={67}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037131292&partnerID=MN8TOARS}, DOI={10.1021/jo025843i}, abstractNote={We describe a two-step conversion of C-alkylated zinc chlorins to zinc oxochlorins wherein the keto group is located in the reduced ring (17-position) of the macrocycle. The transformation proceeds by hydroxylation upon exposure to alumina followed by dehydrogenation with DDQ. The reactions are compatible with ethyne, iodo, ester, trimethylsilyl, and pentafluorophenyl groups. A route to a spirohexyl-substituted chlorin/oxochlorin has also been developed. Representative chlorins and oxochlorins were characterized by static and time-resolved absorption spectroscopy and fluorescence spectroscopy, resonance Raman spectroscopy, and electrochemistry. The fluorescence quantum yields of the zinc oxochlorins (Phi(f) = 0.030-0.047) or free base (Fb) oxochlorins (Phi(f) = 0.13-0.16) are comparable to those of zinc tetraphenylporphyrin (ZnTPP) or free base tetraphenylporphyrin (FbTPP), respectively. The excited-state lifetimes of the zinc oxochlorins (tau = 0.5-0.7 ns) are on average 4-fold lower than that of ZnTPP, and the lifetimes of the Fb oxochlorins (tau = 7.4-8.9 ns) are approximately 40% shorter than that of FbTPP. Time-resolved absorption spectroscopy of a zinc oxochlorin indicates the yield of intersystem crossing is >70%. Resonance Raman spectroscopy of copper oxochlorins show strong resonance enhancement of the keto group upon Soret excitation but not with Q(y)()-band excitation, which is attributed to the location of the keto group in the reduced ring (rather than in the isocyclic ring as occurs in chlorophylls). The one-electron oxidation potential of the zinc oxochlorins is shifted to more positive potentials by approximately 240 mV compared with that of the zinc chlorin. Collectively, the fluorescence yields, excited-state lifetimes, oxidation potentials, and various spectral characteristics of the chlorin and oxochlorin building blocks provide the foundation for studies of photochemical processes in larger architectures based on these chromophores.}, number={21}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Taniguchi, M and Kim, HJ and Ra, DY and Schwartz, JK and Kirmaier, C and Hindin, E and Diers, JR and Prathapan, S and Bocian, DF and Holten, D and et al.}, year={2002}, month={Oct}, pages={7329–7342} } @article{taniguchi_ra_mo_balasubramanian_lindsey_2001, title={Synthesis of meso-substituted chlorins via tetrahydrobilene-a intermediates}, volume={66}, ISSN={["0022-3263"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035798224&partnerID=MN8TOARS}, DOI={10.1021/jo0104835}, abstractNote={Chlorin building blocks incorporating a geminal dimethyl group in the reduced ring and synthetic handles in specific patterns at the perimeter of the macrocycle are expected to have utility in biomimetic and materials chemistry. A prior route employed condensation of a dihydrodipyrrin (Western half) and a bromodipyrromethane-monocarbinol (Eastern half), followed by oxidative cyclization of the putative dihydrobilene-a to form the meso-substituted zinc chlorin in yields of approximately 10%. The limited stability of the dihydrodipyrrin precluded study of the chlorin-forming process. We now have refined this methodology. A tetrahydrodipyrrin Western half (2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin) has been synthesized and found to be quite stable. The condensation of the Western half and an Eastern half (100 mM each) proceeded smoothly in CH(3)CN containing 100 mM TFA at room temperature for 30 min. The resulting linear tetrapyrrole, a 2,3,4,5-tetrahydrobilene-a, also is quite stable, enabling study of the conversion to chlorin. Refined conditions for the oxidative cyclization were found to include the following: the tetrahydrobilene-a (10 mM), AgTf (3-5 molar equiv), Zn(OAc)(2) (15 molar equiv), and 2,2,6,6-tetramethylpiperidine (15 molar equiv) in CH(3)CN at reflux exposed to air for 4-6 h, affording the zinc chlorin. The chlorin-forming process could be implemented in either a two-flask process or a one-flask process. The two-flask process was applied to form six zinc chlorins bearing substituents such as pentafluorophenyl, 3,5-di-tert-butylphenyl, TMS-ethyl benzoate, iodophenyl, or ethynylphenyl (deprotection of the TMS-ethynyl group occurred during the oxidative cyclization process). The stepwise yields (isolated) for the condensation and oxidative cyclization processes forming the tetrahydrobilene and zinc chlorin were 32-72% and 27-62%, respectively, giving overall yields of zinc chlorin from the Eastern and Western halves of 12-45%. Taken together, the refinements introduced enable 100-mg quantities of chlorin building blocks to be prepared in a facile and rational manner.}, number={22}, journal={JOURNAL OF ORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Taniguchi, M and Ra, D and Mo, G and Balasubramanian, T and Lindsey, JS}, year={2001}, month={Nov}, pages={7342–7354} } @article{taniguchi_thiemann_sawada_mataka_1999, title={Layered [3.3]Orthocyclophane Tricarbonylchromium Complexes}, volume={625}, DOI={10.1002/(sici)1521-3749(199908)625:8<1249::aid-zaac1249>3.0.co;2-o}, abstractNote={The preparation of the layered [3.3]orthocyclophane tricarbonylchromium mono- and bis complexes, 4 and 5, are described. X-ray crystallographic analysis reveals the fact that the distances and the dihedral angle between the planes of the two benzo rings in mono complex 4 decrease as compared to those in 1. This is due to the decrease in π electron density in one benzo unit.}, number={8}, journal={Zeitschrift für anorganische und allgemeine Chemie}, publisher={Wiley}, author={Taniguchi, Masahiko and Thiemann, Thies and Sawada, Tsuyoshi and Mataka, Shuntaro}, year={1999}, month={Aug}, pages={1249–1251} } @article{isobe_taniguchi_sawada_thiemann_yonemitsu_mataka_1999, title={Novel rearrangement of conformationally restrained [3.3]orthocyclophanes}, DOI={10.1039/a903156a}, abstractNote={Novel rearrangement of intermediate carbocations generated from rigid, layered [3.3]orthocyclophane-alcohols 4 are presented. The bicyclo[4.4.1]undecane framework of 4 rearranges to either bicyclo[5.4.0]- 5 and/or bicyclo[4.4.0]- 6 or tricyclo[5.4.0.02,11]- ring-system 11, depending upon the nature of the aryl substituent on the bridging tertiary carbon atom. X-Ray crystal structure analyses have been performed on the rearrangement products.}, number={15}, journal={Journal of the Chemical Society, Perkin Transactions 1}, publisher={Royal Society of Chemistry (RSC)}, author={Isobe, Shin-ichiro and Taniguchi, Masahiko and Sawada, Tsuyoshi and Thiemann, Thies and Yonemitsu, Tadashi and Mataka, Shuntaro}, year={1999}, pages={2101–2108} } @article{tsukamoto_sahade_taniguchi_sawada_thiemann_mataka_1999, title={Synthesis of 8,16-dimethyl- and 8,16-dimethoxy-5,13-di-t-butyl[2.2]metacyclophane-1,2,9,10-tetraone}, volume={40}, DOI={10.1016/s0040-4039(99)00845-x}, abstractNote={Swern oxidation of 8,16-dimethoxy- and 8,16-dimethyl-5,13-di-t-butyl-1,2,9,10-tetrahydroxy[2.2]metacyclophane, 1 and 2, afforded 5,13-di-t-butyl-10-hydroxy-8,16-dimethoxy[2.2]metacyclophane-1,2,9-trione 3 and 4. By subsequent oxidation with DDQ, 8,16-dimethoxy- and 8,16-dimethyl-5,13-di-t-butyl[2.2]metacyclophane-1,2,9,10-tetraones, 5 and 6, were obtained.}, number={25}, journal={Tetrahedron Letters}, publisher={Elsevier BV}, author={Tsukamoto, Ken-ichi and Sahade, Daniel A. and Taniguchi, Masahiko and Sawada, Tsuyoshi and Thiemann, Thies and Mataka, Shuntaro}, year={1999}, month={Jun}, pages={4691–4692} } @article{thiemann_ohira_li_sawada_taniguchi_tashiro_mataka_1999, title={Thieno[3.3]orthocyclophanes: preparations and structures}, volume={23}, DOI={10.1039/a903746b}, abstractNote={Rigid, layered hetareno/hetareno- and hetareno/areno-cyclophanes with closely held, non-distorted, interacting π-systems can be synthesized easily by using various building blocks.}, number={7}, journal={New Journal of Chemistry}, publisher={Royal Society of Chemistry (RSC)}, author={Thiemann, Thies and Ohira, Daisuke and Li, Yuanquiang and Sawada, Tsuyoshi and Taniguchi, Masahiko and Tashiro, Masashi and Mataka, Shuntaro}, year={1999}, pages={675–678} } @article{mataka_mitoma_sawada_thiemann_taniguchi_tashiro_1998, title={Benzo[3.3]benzo[3.3]benzo- and naphtho[3.3]benzo[3.3]naphtho-orthocyclophane bis(alcohol)s. Preparations and structures}, volume={54}, DOI={10.1016/s0040-4020(98)00217-8}, abstractNote={anti-Benzo[1,2-h;4,5-h′]bis(benzo[1,2-c]bicyclo[4.4.1]undeca-3,8-diene-11-one) (7a and bis(naphtho[2,3-c]bicyclo[4.4.1]undeca-3,8-diene-11-one) derivative 7b reacted with Grignard reagents (MeMgI and PhMgBr) to give bis(alcohol)s 10–12 or monoalcohols 13 and 14, depending upon the amount of the reagent used. Similarly, syn-bis(alcohol)s 15–17 and syn-monoalcohols 18 and 19 were obtained in the reaction of syn-benzo[1,2-h;4,5-h′]bis(benzo[1,2-c]bicyclo[4.4.1]undeca-3,8-diene-11-one) (9) with the Grignard reagents. The alcohols 10–19 were produced as a mixture of configurational isomers and each isomer was isolated by HPLC. The structures were determined by 1H and 13C NMR spectra, NOE study, and X-ray crystallographic analyses of 12a, 13, and 17a. The triple-layered [3.3][3.3]orthocyclophanes 10–12 take the (twin-chair)/(twin-chair) arrangement and in the structure, the top and the bottom aromatic rings sandwich a central benzo ring. syn-Cyclophanes 15–17 exist as an equilibrium mixture of two equivalent (twin-chair)/(chair-boat)- and (chair-boat)/(twin-chair)-conformers in solution. In the solid, the conformation is fixed, as clarified by X-ray crystallographic analysis of 17a. Because of steric congestion, the central benzene ring in 17a is not planar. Monoalcohols 13–14 and 18–19 have a rigid and layered twin-chair substructure and a flexible chair-boat part. The existence of a through-space interaction between the three stacked aromatic rings of [3.3][3.3]orthocyclophanes 10–12 was determined on the basis of a long wavelength shift in UV spectra, as compared to the spectra of 13–19 having a double-layered [3.3]orthocyclophane-substructure.}, number={20}, journal={Tetrahedron}, publisher={Elsevier BV}, author={Mataka, Shuntaro and Mitoma, Yoshiharu and Sawada, Tsuyoshi and Thiemann, Thies and Taniguchi, Masahiko and Tashiro, Masashi}, year={1998}, month={May}, pages={5171–5186} } @article{mataka_shigaki_sawada_mitoma_taniguchi_thiemann_ohga_egashira_1998, title={Quadrupeldecker-[3.3][3.3][3.3]Orthocyclophanacetal: eine Orthocyclophan-Leiter}, volume={110}, DOI={10.1002/(sici)1521-3757(19980918)110:18<2626::aid-ange2626>3.0.co;2-s}, abstractNote={Durch geschicktes Verbrücken von Orthocyclophanen (hier durch Acetalisierung) werden Verbindungen wie 1 erhalten, in denen vier Benzolringe in einer starren Fläche-auf-Fläche-Anordnung übereinandergestapelt sind. UV-spektroskopische Daten und die elektrochemischen Eigenschaften von 1 belegen das Vorliegen von π-π-Through-space-Wechselwirkungen innerhalb des Moleküls.}, number={18}, journal={Angewandte Chemie}, publisher={Wiley}, author={Mataka, Shuntaro and Shigaki, Kouichiro and Sawada, Tsuyoshi and Mitoma, Yoshihara and Taniguchi, Masahiko and Thiemann, Thies and Ohga, Kazuya and Egashira, Naoyoshi}, year={1998}, month={Sep}, pages={2626–2628} } @article{mataka_shigaki_sawada_mitoma_taniguchi_thiemann_ohga_egashira_1998, title={Quadruple Decker [3.3][3.3][3.3]Orthocyclophane Acetal—An Orthocyclophane Ladder}, volume={37}, DOI={10.1002/(sici)1521-3773(19981002)37:18<2532::aid-anie2532>3.0.co;2-r}, abstractNote={Through clever bridging of orthocyclophanes (in this case by acetalization), molecules such as 1 can be formed with four benzene rings in a stacked face-to-face arrangement. UV/Vis spectroscopic and electrochemical properties of 1 are governed by π-π through-space interactions within the molecule.}, number={18}, journal={Angewandte Chemie International Edition}, publisher={Wiley}, author={Mataka, Shuntaro and Shigaki, Kouichiro and Sawada, Tsuyoshi and Mitoma, Yoshihara and Taniguchi, Masahiko and Thiemann, Thies and Ohga, Kazuya and Egashira, Naoyoshi}, year={1998}, month={Oct}, pages={2532–2534} } @article{hashimoto_hatano_minabe_iyo_taniguchi_hoshino_sakiyama_kawasumi_1998, title={Radiosynthesis of [18F]N-(4-phenylbutyl)-4-(4-fluorobenzoyl)piperidine for studying serotonin 5-HT2a receptors}, volume={41}, DOI={10.1002/(sici)1099-1344(1998100)41:10<941::aid-jlcr151>3.0.co;2-6}, abstractNote={N-(4-Phenylbutyl)-4-(4-fluorobenzoyl)piperidine [4-PBFBP] shows highly selective binding to serotonin 5-HT 2A receptors with high affinity. In this study, we prepared [ 18 F]4-PBFBP for in vivo study of 5-HT 2A receptors in the brain using positron emission tomography (PET). Nucleophilic aromatic displacement of N-(4-phenylbutyl)-4-(4-nitrobenzoyl)piperidine by no carrier added [ 18 F]fluoride which was solubilized by Kryptofix 222 in DMSO produced [ 18 F]4-PBFBP with high specific radioactivity. The product was purified by reversed phase preparative HPLC and was extracted from the collected eluate by SEP-PAK® C18 cartridge prior to formulation. The radiochemical yield of the final product was 15 ± 1.8 % (mean ± S.D. of three experiments) with decay correction and the specific activity was 113 ± 27 GBq/μmol (mean ± S.D. of three experiments) at E.O.S. after a total preparation time of about 160 min. The radiochemical purity of [ 18 F]4-PBFBP was more than 99 %. The regional distribution of [ 18 F]4-PBFBP in mouse brain was also examined.}, number={10}, journal={Journal of Labelled Compounds and Radiopharmaceuticals}, publisher={Wiley}, author={Hashimoto, Kenji and Hatano, Kentaro and Minabe, Yoshio and Iyo, Masaomi and Taniguchi, Masahiko and Hoshino, Osamu and Sakiyama, Yojiro and Kawasumi, Yasuhiro}, year={1998}, month={Oct}, pages={941–949} } @article{taniguchi_mataka_thiemann_sawada_mimura_mitoma_1998, title={The Study of π–π Interaction in Layered [3.3]Orthocyclophanes. Charge-Transfer Complexes of [3.3]Orthocyclophanes with Tetracyanoethylene}, volume={71}, DOI={10.1246/bcsj.71.2661}, abstractNote={Abstract Dibenzo[3.3]orthocyclophanes ([3.3]OCPs) with a bicyclo[4.4.1]undecane substructure form charge-transfer (C-T) complexes with tetracyanoethylene (TCNE). 3,4 : 8,9-Dibenzobicyclo[4.4.1]undecane (9) and its 11-methylene derivative 8 are flexible molecules and take a chair-boat conformation. Complexes 8- and 9-TCNE exhibit the absorption maximum at ca. 420 nm, which coincides with the value for the TCNE complex of o-xylene. On the other hand, acetal 5, methylcarbinol 6, and dimethylmethylene derivative 7 are rigid, layered [3.3]OCPs with stacked benzene rings. Compounds 5, 6, and 7 form a 1 : 1 complex with TCNE in solution. The absorption maxima of the complexes at ca. 500 nm suggest an enhanced C-T complexation due to a π–π through-space interaction in 5, 6, and 7. A 2 : 1 complex of rigid [3.3]OCP 7 with TCNE crystallized from dichloromethane, while OCP 8 gave a red crystalline 2 : 3 complex with TCNE. X-ray crystallographic analyses of these two complexes is given.}, number={11}, journal={Bulletin of the Chemical Society of Japan}, publisher={The Chemical Society of Japan}, author={Taniguchi, Masahiko and Mataka, Shuntaro and Thiemann, Thies and Sawada, Tsuyoshi and Mimura, Keisuke and Mitoma, Yoshiharu}, year={1998}, month={Nov}, pages={2661–2668} } @article{mataka_mitoma_thiemann_sawada_taniguchi_kobuchi_tashiro_1997, title={Bisacetals of aromatic ring-annelated . [3.3][3.3]Orthocyclophanes with triple-layered benzo/benzo/benzo- and naphtho/benzo/naphtho-system}, volume={53}, DOI={10.1016/s0040-4020(97)00042-2}, abstractNote={Abstract Tetraesters anti - 9a,b and syn - 9a,b , which have three aromatic rings, were prepared by the reaction of benzocycloheptenediester 7 with 1,2,4,5-tetrakis(bromomethyl)benzene. Subsequent hydrolysis and pyrolysis gave diketones anti - 11a,b and syn - 11a,b , which were acetalized to yield bisacetals anti - 5a,b and syn - 5a,b . X-Ray crystallographic analyses indicate a symmetric (twin-chair)/(twin-chair)-conformation of anti - 5a,b , in which two naphtho or benzo rings sandwich one benzene ring. Anti - 5a and anti - 5b 9b) are rigid structures. The protons of their central aromatic rings show an up-field shift, due to an anisotropic effect of the facing outer aromatic units. In contrast, syn - 5a,b are flexible structures. The UV-spectra of anti - 5a,b show a long wavelength shift, as compared to syn - 5a,b , suggesting a through-space interaction among the aromatic rings.}, number={9}, journal={Tetrahedron}, publisher={Elsevier BV}, author={Mataka, Shuntaro and Mitoma, Yoshiharu and Thiemann, Thies and Sawada, Tsuyoshi and Taniguchi, Masahiko and Kobuchi, Masaru and Tashiro, Masashi}, year={1997}, month={Mar}, pages={3015–3026} } @article{mataka_sawada_tashiro_taniguchi_mitroma_1997, title={Conformational Analysis of Spirocyclopropane- and Spirooxirane-annelated Dibenzobicyclo[4.4.1]undecanes by 1H NMR Spectroscopy and X-Ray Crystallography}, DOI={10.1039/a604939g}, abstractNote={Conformational behaviour of dibenzo[c,h]bicyclo[4.4.1]undecanes having a dichloro- and a dibromo-cyclopropane ring, together with an oxirane ring on the methylene bridge, has been studied by 1 H NMR spectroscopy and X-ray crystallography.}, number={2}, journal={Journal of Chemical Research}, publisher={Royal Society of Chemistry (RSC)}, author={Mataka, Shuntaro and Sawada, Tsuyoshi and Tashiro, Masahi and Taniguchi, Masahiko and Mitroma, Yoshiharu}, year={1997}, pages={48–49} } @article{mataka_mitoma_sawada_tashiro_1996, title={Triple-layered orthonaphtho[3.3]orthobenzeno[3.3]orthonaphthophane}, volume={37}, DOI={10.1016/0040-4039(95)02103-5}, abstractNote={Triple-layered [3.3][3.3]orthocyclophane of the anti-type was prepared for the first time, and its structure, in which two naphthalene rings sandwitch one benzene ring, was established by X-ray crystallographic analysis.}, number={1}, journal={Tetrahedron Letters}, publisher={Elsevier BV}, author={Mataka, Shuntaro and Mitoma, Yoshiharu and Sawada, Tsuyoshi and Tashiro, Masashi}, year={1996}, month={Jan}, pages={65–68} }