@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={Understanding 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 (beta) 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={Abstract The 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 Q y 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 Q y 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 ( B y , B x , Q x , Q y ) 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{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 131-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 α-arylation closed the isocyclic ring to give the 131-oxophorbine (2) in 85% yield. Facile access to 131-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} }
 @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·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 Qy band (606−662 nm), (2) a relative increase in the intensity of the Qy band (IB/IQ = 4.2−1.5), and (3) an increase in the fluorescence quantum yield Φf (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{carcel_laha_loewe_thamyongkit_schweikart_misra_bocian_lindsey_2004, title={Porphyrin architectures tailored for studies of molecular information storage}, volume={69}, ISSN={["0022-3263"]}, DOI={10.1021/jo0498260}, abstractNote={A molecular approach to information storage employs redox-active molecules tethered to an electroactive surface. Zinc porphyrins tethered to Au(111) or Si(100) provide a benchmark for studies of information storage. Three sets of porphyrins have been synthesized for studies of the interplay of molecular design and charge-storage properties: (1) A set of porphyrins is described for probing the effect of surface attachment atom on electron-transfer kinetics. Each porphyrin bears a meso-CH2X group for surface attachment where X = OH, SAc, or SeAc. (2) A set of porphyrins is described for studying the effect of surface-charge density in monolayers. Each porphyrin bears a benzyl alcohol for surface attachment and three nonlinking meso substituents of a controlled degree of bulkiness. (3) A set of porphyrins is described that enables investigation of on-chip patterning of the electrolyte. Each porphyrin bears a formyl group distal to the surface attachment group for subsequent derivatization with a molecular entity that comprises the electrolyte. Taken together, this collection of molecules enables a variety of studies to elucidate design issues in molecular-based information storage.}, number={20}, journal={JOURNAL OF ORGANIC CHEMISTRY}, author={Carcel, CM and Laha, JK and Loewe, RS and Thamyongkit, P and Schweikart, KH and Misra, V and Bocian, DF and Lindsey, JS}, year={2004}, month={Oct}, pages={6739–6750} }
 @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} }