@article{zhang_reddy_mass_kim_hu_lindsey_2017, title={Synthesis of tailored hydrodipyrrins and their examination in directed routes to bacteriochlorins and tetradehydrocorrins}, volume={41}, DOI={10.1039/c7nj01892d}, abstractNote={18 gem-dimethyl stabilized hydrodipyrrins with diverse α-substituents have been prepared and examined in directed syntheses of unsymmetrically substituted hydroporphyrins.}, number={19}, journal={New Journal of Chemistry}, author={Zhang, S. F. and Reddy, M. N. and Mass, O. and Kim, H. J. and Hu, G. F. and Lindsey, Jonathan}, year={2017}, pages={11170–11189} }
 @article{zhang_kim_tang_yang_bocian_holten_lindsey_2016, title={Synthesis and photophysical characteristics of 2,3,12,13-tetraalkylbacteriochlorins}, volume={40}, ISSN={["1369-9261"]}, DOI={10.1039/c6nj00517a}, abstractNote={Tetraalkylbacteriochlorins, available upon acid-mediated self-condensation of α-ester stabilized dihydrodipyrrin-carboxaldehydes, provide valuable models of the naturally occurring bacteriochlorophylls.}, number={7}, journal={NEW JOURNAL OF CHEMISTRY}, author={Zhang, Shaofei and Kim, Han-Je and Tang, Qun and Yang, Eunkyung and Bocian, David F. and Holten, Dewey and Lindsey, Jonathan S.}, year={2016}, month={Jul}, pages={5942–5956} }
 @article{aravindu_krayer_kim_lindsey_2011, title={Facile synthesis of a B,D-tetradehydrocorrin and rearrangement to bacteriochlorins}, volume={35}, number={7}, journal={New Journal of Chemistry}, author={Aravindu, K. and Krayer, M. and Kim, H. J. and Lindsey, J. S.}, year={2011}, pages={1376–1384} }
 @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{krayer_yang_kim_kee_deans_sluder_diers_kirmaier_bocian_holten_et al._2011, title={Synthesis and Photophysical Characterization of Stable Indium Bacteriochlorins}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic200325d}, abstractNote={Bacteriochlorins have wide potential in photochemistry because of their strong absorption of near-infrared light, yet metallobacteriochlorins traditionally have been accessed with difficulty. Established acid-catalysis conditions [BF3·OEt2 in CH3CN or TMSOTf/2,6-di-tert-butylpyridine in CH2Cl2] for the self-condensation of dihydrodipyrrin-acetals (bearing a geminal dimethyl group in the pyrroline ring) afford stable free base bacteriochlorins. Here, InBr3 in CH3CN at room temperature was found to give directly the corresponding indium bacteriochlorin. Application of the new acid catalysis conditions has afforded four indium bacteriochlorins bearing aryl, alkyl/ester, or no substituents at the β-pyrrolic positions. The indium bacteriochlorins exhibit (i) a long-wavelength absorption band in the 741−782 nm range, which is shifted bathochromically by 22−32 nm versus the analogous free base species, (ii) fluorescence quantum yields (0.011−0.026) and average singlet lifetime (270 ps) diminished by an order of magnitude versus that (0.13−0.25; 4.0 ns) for the free base analogues, and (iii) higher average yield (0.9 versus 0.5) yet shorter average lifetime (30 vs 105 μs) of the lowest triplet excited state compared to the free base compounds. The differences in the excited-state properties of the indium chelates versus free base bacteriochlorins derive primarily from a 30-fold greater rate constant for S1 → T1 intersystem crossing, which stems from the heavy-atom effect on spin−orbit coupling. The trends in optical properties of the indium bacteriochlorins versus free base analogues, and the effects of 5-OMe versus 5-H substituents, correlate well with frontier molecular-orbital energies and energy gaps derived from density functional theory calculations. Collectively the synthesis, photophysical properties, and electronic characteristics of the indium bacteriochlorins and free base analogues reported herein should aid in the further design of such chromophores for diverse applications.}, number={10}, journal={INORGANIC CHEMISTRY}, author={Krayer, Michael and Yang, Eunkyung and Kim, Han-Je and Kee, Hooi Ling and Deans, Richard M. and Sluder, Camille E. and Diers, James R. and Kirmaier, Christine and Bocian, David F. and Holten, Dewey and et al.}, year={2011}, month={May}, pages={4607–4618} }
 @article{krayer_ptaszek_kim_meneely_fan_secor_lindsey_2010, title={Expanded Scope of Synthetic Bacteriochlorins via Improved Acid Catalysis Conditions and Diverse Dihydrodipyrrin-Acetals}, volume={75}, ISSN={["0022-3263"]}, DOI={10.1021/jo9025572}, abstractNote={Bacteriochlorins are attractive candidates for a wide variety of photochemical studies owing to their strong absorption in the near-infrared spectral region. The prior acid-catalysis conditions [BF(3) x O(Et)(2) in CH(3)CN at room temperature] for self-condensation of a dihydrodipyrrin-acetal (bearing a geminal dimethyl group in the pyrroline ring) typically afforded a mixture of three macrocycles: the expected 5-methoxybacteriochlorin (MeOBC-type), a 5-unsubstituted bacteriochlorin (HBC-type), and a free base B,D-tetradehydrocorrin (TDC-type). Here, a broad survey of >20 acids identified four promising acid catalysis conditions of which TMSOTf/2,6-di-tert-butylpyridine in CH(2)Cl(2) at room temperature was most attractive owing to formation of the 5-methoxybacteriochlorin as the sole macrocycle regardless of the pyrrolic substituents in the dihydrodipyrrin-acetal (electron-withdrawing, electron-donating, or no substituent). Eleven new dihydrodipyrrin-acetals were prepared following standard routes. Application of the new acid catalysis conditions has afforded diverse bacteriochlorins (e.g., bearing alkyl/ester, aryl/ester, diester, and no substituents) in a few days from commercially available starting materials. Consideration of the synthetic steps and yields for formation of the dihydrodipyrrin-acetal and bacteriochlorin underpins evaluation of synthetic plans for early installation of bacteriochlorin substituents via the dihydrodipyrrin-acetal versus late installation via derivatization of beta-bromobacteriochlorins. Treatment of the 5-methoxybacteriochlorins with NBS gave regioselective 15-bromination when no pyrrolic substituents were present or when each pyrrole contained two substituents; on the other hand, the presence of a beta-ethoxycarbonyl group caused loss of regioselectivity. The 15 new bacteriochlorins prepared herein exhibit a long-wavelength absorption band in the range 707-759 nm, providing tunable access to the near-infrared region. Taken together, this study expands the scope of available bacteriochlorins for fundamental studies and diverse applications.}, number={4}, journal={JOURNAL OF ORGANIC CHEMISTRY}, author={Krayer, Michael and Ptaszek, Marcin and Kim, Han-Je and Meneely, Kelly R. and Fan, Dazhong and Secor, Kristen and Lindsey, Jonathan S.}, year={2010}, month={Feb}, pages={1016–1039} }
 @misc{kim_lindsey_2009, title={De novo synthesis of bacteriochlorins}, volume={7,534,807}, number={2009 May 19}, author={Kim, H.-J. and Lindsey, J. S.}, year={2009} }
 @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), and Pd(II)] including the chlorin lacking any β-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{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={The 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{kim_dogutan_ptaszek_lindsey_2007, title={Synthesis of hydrodipyrrins tailored for reactivity at the 1- and 9-positions}, volume={63}, ISSN={["0040-4020"]}, DOI={10.1016/j.tet.2006.10.027}, abstractNote={A collection of 33 hydrodipyrrins (9 targets, 21 intermediates, and 3 byproducts) has been prepared. The hydrodipyrrins (dihydrodipyrrins, tetrahydrodipyrrins, and hexahydrodipyrrins) contain a pyrrole ring and a geminal-dimethyl substituted 1-pyrroline (or pyrrolidine) ring. The α-substituents on the pyrrole ring (H, Br, CHO) and pyrroline ring (H, CH3, CH(OR)2, OMe, SMe) provide different reactivity combinations (Nu−, E+) and 0, 1, or 2 carbon atoms (which can give rise to the bridging meso-carbons in hydroporphyrins). Straightforward access to various hydrodipyrrins should facilitate development of syntheses of diverse hydroporphyrins.}, number={1}, journal={TETRAHEDRON}, author={Kim, Han-Je and Dogutan, Dilek Kiper and Ptaszek, Marcin and Lindsey, Jonathan S.}, year={2007}, month={Jan}, pages={37–55} }
 @article{kim_lindsey_2005, title={De novo synthesis of stable tetrahydroporphyrinic macrocycles: Bacteriochlorins and a tetradehydrocorrin}, volume={70}, ISSN={["0022-3263"]}, DOI={10.1021/jo050467y}, abstractNote={Bacteriochlorins (tetrahydroporphyrins) are attractive for diverse photochemical applications owing to their strong absorption in the near-infrared spectral region, as exemplified by the bacterial photosynthetic pigment bacteriochlorophyll a, yet often are labile toward dehydrogenation to give the chlorin. Tetradehydrocorrins (ring-contracted tetrahydroporphyrins) are attractive for studies of catalysis analogous to that of vitamin B12. An eight-step synthesis toward such tetrahydroporphyrinic macrocycles begins with p-tolualdehyde and proceeds to a dihydrodipyrrin-acetal (1) bearing a geminal dimethyl group and a p-tolyl substituent. Self-condensation of 1 in CH3CN containing BF3·OEt2 at room temperature afforded a readily separable mixture of two free base bacteriochlorins and a free base B,D-tetradehydrocorrin. Each bacteriochlorin contains two geminal dimethyl groups to lock-in the bacteriochlorin hydrogenation level, p-tolyl substituents at opposing (2,12) β-positions, and the absence (H−BC) or presence (MeO−BC) of a methoxy group at the 5- (meso) position. The B,D-tetradehydrocorrin (TDC) lies equidistant between the hydrogenation levels of corrin and corrole, is enantiomeric, and contains two geminal dimethyl groups, 2,12-di-p-tolyl substituents, and an acetal group at the pyrroline−pyrrole junction. Examination of the effect of the concentrations of 1 (2.5−50 mM) and BF3·OEt2 (10−500 mM) revealed a different response surface for each of H−BC, MeO−BC, and TDC, enabling relatively selective preparation of a given macrocycle. The highest isolated yield of each was 49, 30, and 66%, respectively. The macrocycles are stable to routine handling in light and air. The bacteriochlorins display characteristic spectral features; for example, H−BC exhibits near-IR absorption (λQy = 737 nm, εQy = 130 000 M-1 cm-1) and emission (λem = 744 nm, Φf = 0.14). In summary, this simple entry to stable bacteriochlorins and tetradehydrocorrins should facilitate a wide variety of applications.}, number={14}, journal={JOURNAL OF ORGANIC CHEMISTRY}, author={Kim, HJ and Lindsey, JS}, year={2005}, month={Jul}, pages={5475–5486} }
 @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 five-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 NaBH4 to give 2-(2-nitroethyl)pyrrole (4), (iii) Michael addition of 4 with mesityl oxide under neat conditions or at high concentration to give γ-nitrohexanone-pyrrole 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} }
 @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{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} }