@article{mandal_sahin_liu_lindsey_bocian_holten_2016, title={Photophysical comparisons of PEGylated porphyrins, chlorins and bacteriochlorins in water}, volume={40}, ISSN={["1369-9261"]}, DOI={10.1039/c6nj02091g}, abstractNote={Comparison of the photophysics of analogous members of the porphyrin, chlorin, and bacteriochlorin family has rarely been carried out, and most studies of individual members have been performed in non-aqueous media. Advances in synthesis and molecular design now enable such comparative studies in aqueous solution. A water-soluble bioconjugatable free base porphyrin (FbP1) has been synthesized, complementing recently prepared chlorin and bacteriochlorin analogues. The porphyrin (a trans-AB architecture; i.e., 5,15-substitution pattern) is equipped with one meso-aryl group that bears three short polyethylene glycol (PEG) substituents at the 2,4,6-positions for aqueous solubility, and one meso-aryl group that bears an oxyacetic acid group at the p-position for bioconjugation. Spectroscopic examination of porphyrin FbP1 gave the following quantum yields in DMF versus water: fluorescence (Φf = 0.077 vs. 0.066), intersystem crossing (Φisc = 0.90 vs. 0.84), and internal conversion (Φic = 0.023 vs. 0.094). The increase in Φic upon moving from DMF into water reflects the 4-fold increase in rate constant for internal conversion, from (600 ns)−1 to (140 ns)−1. Photophysical comparisons (τS, kf, kic, kisc, Φf, Φic, Φisc) were made with analogous chlorins and bacteriochlorins in DMF and water. The value of kic in both media increases in the order (visible-absorbing) porphyrin < (red-absorbing) chlorin < (near-infrared-absorbing) bacteriochlorin, consistent with the general S1-energy dependence of kic expected on the basis of the energy-gap law for non-radiative decay. In summary, there are now satisfactory molecular designs, viable synthetic routes, and thoroughly characterized photophysical properties that permit aqueous solution studies of a complement of porphyrins, chlorins, and bacteriochlorins.}, number={11}, journal={NEW JOURNAL OF CHEMISTRY}, author={Mandal, Amit Kumar and Sahin, Tuba and Liu, Mengran and Lindsey, Jonathan S. and Bocian, David F. and Holten, Dewey}, year={2016}, pages={9648–9656} }
 @article{adams_collins_sahin_subramanian_urban_vairaprakash_tian_evans_shreve_montano_2015, title={Diblock Copolymer Micelles and Supported Films with Noncovalently Incorporated Chromophores: A Modular Platform for Efficient Energy Transfer}, volume={15}, ISSN={["1530-6992"]}, DOI={10.1021/nl504814x}, abstractNote={We report generation of modular, artificial light-harvesting assemblies where an amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(butadiene), serves as the framework for noncovalent organization of BODIPY-based energy donor and bacteriochlorin-based energy acceptor chromophores. The assemblies are adaptive and form well-defined micelles in aqueous solution and high-quality monolayer and bilayer films on solid supports, with the latter showing greater than 90% energy transfer efficiency. This study lays the groundwork for further development of modular, polymer-based materials for light harvesting and other photonic applications.}, number={4}, journal={NANO LETTERS}, author={Adams, Peter G. and Collins, Aaron M. and Sahin, Tuba and Subramanian, Vijaya and Urban, Volker S. and Vairaprakash, Pothiappan and Tian, Yongming and Evans, Deborah G. and Shreve, Andrew P. and Montano, Gabriel A.}, year={2015}, month={Apr}, pages={2422–2428} }
 @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{sahin_vairaprakash_borbas_balasubramanian_lindsey_2015, title={Hydrophilic bioconjugatable trans-AB-porphyrins and peptide conjugates}, volume={19}, ISSN={["1099-1409"]}, DOI={10.1142/s1088424615500121}, abstractNote={Porphyrins bearing a single bioconjugatable group and a single water-solubilization motif in a trans-AB-architecture (with no other substituents) provide a compact design of value for studies in diverse disciplines. Established synthetic methods have been employed to prepare four new free base porphyrins and one Mn(III) chelate. The hydrophilic motif includes 4-N-methylpyridinium, 2,4,6-tris(carboxymethoxy)phenyl, 2,6-bis(phosphonomethoxy)phenyl, and carboxy; the bioconjugatable unit includes carboxy, maleimido, and N-hydroxysuccinimido (NHS) ester. Bioconjugation experiments with a protected porphyrin-diphosphate or unprotected porphyrin-diphosphonate were examined in organic solution or water, respectively. Both approaches were employed to conjugate to the e-amino group of Lys11 in AcKPV-NH2, a tripeptide fragment [Ac-α-MSH(11-13)-NH2] of melanocyte stimulating hormone, yielding porphyrin-peptide conjugates.}, number={5}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, author={Sahin, Tuba and Vairaprakash, Pothiappan and Borbas, K. Eszter and Balasubramanian, Thiagarajan and Lindsey, Jonathan S.}, year={2015}, month={May}, pages={663–678} }
 @article{sahin_harris_vairaprakash_niedzwiedzki_subramanian_shreve_bocian_holten_lindsey_2015, title={Self-Assembled Light-Harvesting System from Chromophores in Lipid Vesicles}, volume={119}, ISSN={["1520-5207"]}, DOI={10.1021/acs.jpcb.5b04841}, abstractNote={Lipid vesicles are used as the organizational structure of self-assembled light-harvesting systems. Following analysis of 17 chromophores, six were selected for inclusion in vesicle-based antennas. The complementary absorption features of the chromophores span the near-ultraviolet, visible, and near-infrared region. Although the overall concentration of the pigments is low (~1 μM for quantitative spectroscopic studies) in a cuvette, the lipid-vesicle system affords high concentration (≥10 mM) in the bilayer for efficient energy flow from donor to acceptor. Energy transfer was characterized in 13 representative binary mixtures using static techniques (fluorescence-excitation versus absorptance spectra, quenching of donor fluorescence, modeling emission spectra of a mixture versus components) and time-resolved spectroscopy (fluorescence, ultrafast absorption). Binary donor-acceptor systems that employ a boron-dipyrrin donor (S0 ↔ S1 absorption/emission in the blue-green) and a chlorin or bacteriochlorin acceptor (S0 ↔ S1 absorption/emission in the red or near-infrared) have an average excitation-energy-transfer efficiency (ΦEET) of ~50%. Binary systems with a chlorin donor and a chlorin or bacteriochlorin acceptor have ΦEET ∼ 85%. The differences in ΦEET generally track the donor-fluorescence/acceptor-absorption spectral overlap within a dipole-dipole coupling (Förster) mechanism. Substantial deviation from single-exponential decay of the excited donor (due to the dispersion of donor-acceptor distances) is expected and observed. The time profiles and resulting ΦEET are modeled on the basis of (Förster) energy transfer between chromophores relatively densely packed in a two-dimensional compartment. Initial studies of two ternary and one quaternary combination of chromophores show the enhanced spectral coverage and energy-transfer efficacy expected on the basis of the binary systems. Collectively, this approach may provide one of the simplest designs for self-assembled light-harvesting systems that afford broad solar collection and efficient energy transfer.}, number={32}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Sahin, Tuba and Harris, Michelle A. and Vairaprakash, Pothiappan and Niedzwiedzki, Dariusz M. and Subramanian, Vijaya and Shreve, Andrew P. and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2015}, month={Aug}, pages={10231–10243} }
 @article{harris_sahin_jiang_vairaprakash_parkes-loach_niedzwiedzki_kirmaier_loach_bocian_holten_et al._2014, title={Enhanced Light-Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1-like Antennas}, volume={90}, ISSN={["1751-1097"]}, DOI={10.1111/php.12319}, abstractNote={Biohybrid light‐harvesting antennas are an emerging platform technology with versatile tailorability for solar‐energy conversion. These systems combine the proven peptide scaffold unit utilized for light harvesting by purple photosynthetic bacteria with attached synthetic chromophores to extend solar coverage beyond that of the natural systems. Herein, synthetic unattached chromophores are employed that partition into the organized milieu (e.g. detergent micelles) that house the LH1‐like biohybrid architectures. The synthetic chromophores include a hydrophobic boron‐dipyrrin dye (A1) and an amphiphilic bacteriochlorin (A2), which transfer energy with reasonable efficiency to the bacteriochlorophyll acceptor array (B875) of the LH1‐like cyclic oligomers. The energy‐transfer efficiencies are markedly increased upon covalent attachment of a bacteriochlorin (B1 or B2) to the peptide scaffold, where the latter likely acts as an energy‐transfer relay site for the (potentially diffusing) free chromophores. The efficiencies are consistent with a Förster (through‐space) mechanism for energy transfer. The overall energy‐transfer efficiency from the free chromophores via the relay to the target site can approach those obtained previously by relay‐assisted energy transfer from chromophores attached at distant sites on the peptides. Thus, the use of free accessory chromophores affords a simple design to enhance the overall light‐harvesting capacity of biohybrid LH1‐like architectures.}, number={6}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, author={Harris, Michelle A. and Sahin, Tuba and Jiang, Jianbing and Vairaprakash, Pothiappan and Parkes-Loach, Pamela S. and Niedzwiedzki, Dariusz M. and Kirmaier, Christine and Loach, Paul A. and Bocian, David F. and Holten, Dewey and et al.}, year={2014}, pages={1264–1276} }
 @article{jiang_vairaprakash_reddy_sahin_pavan_lubian_lindsey_2014, title={Hydrophilic tetracarboxy bacteriochlorins for photonics applications}, volume={12}, ISSN={["1477-0539"]}, DOI={10.1039/c3ob41791c}, abstractNote={Bacteriochlorins absorb strongly in the near-infrared (NIR, 700-900 nm) region and hence are well suited for photophysical studies and photomedical applications, yet such endeavors heretofore have been largely limited by the intrinsic lipophilicity of the bacteriochlorin macrocycle. Here, a new molecular design is investigated wherein 3,5-dicarboxyphenyl units are appended to the β-pyrrolic positions of the bacteriochlorin. Use of the 3,5-aryl substitution motif places the carboxylic acid groups, which are anionic at neutral pH, above and below the plane of the bacteriochlorin macrocycle. A de novo synthesis has been employed to create five such bacteriochlorins, which uses as intermediates two new 2,12-dibromobacteriochlorin building blocks and a known 3,13-dibromobacteriochlorin. The aryl groups with protected carboxylate moieties were introduced by Suzuki coupling; subsequent deprotection afforded the hydrophilic bacteriochlorins. The latter were characterized by absorption and fluorescence spectroscopy in DMF and in aqueous phosphate buffer (pH 7). In most cases, comparable sharp emission (FWHM of ∼25 nm) and modest fluorescence yields (0.060-0.11) were observed in aqueous phosphate buffer medium and in DMF. Aqueous solubility was examined by absorption spectral interrogation of samples over a 1000-fold concentration range with reciprocal change in pathlength (∼0.5, 5, 50, and 500 μM; 10, 1, 0.1, and 0.01 cm pathlength cuvettes). One hydrophilic bacteriochlorin was prepared that contains a single maleimido-terminated tether for bioconjugation; the tether was installed by the sequence of 15-bromination of the bacteriochlorin, Suzuki coupling, and DCC-mediated amide formation. The maleimido-bacteriochlorin was conjugated to a 48-residue cysteine-containing peptide analogue of a constituent from a bacterial photosynthetic light-harvesting complex. Taken together, the results show a new molecular design and facile de novo synthetic route for obtaining hydrophilic bacteriochlorins including a bioconjugatable group if desired.}, number={1}, journal={ORGANIC & BIOMOLECULAR CHEMISTRY}, author={Jiang, Jianbing and Vairaprakash, Pothiappan and Reddy, Kanumuri Ramesh and Sahin, Tuba and Pavan, M. Phani and Lubian, Elisa and Lindsey, Jonathan S.}, year={2014}, month={Jan}, pages={86–103} }