@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 ε-amino group of Lys 11 in AcKPV- NH 2 , a tripeptide fragment [ Ac -α-MSH(11-13)- NH 2 ] 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{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} }
 @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{huang_huang_mroz_tegos_zhiyentayev_sharma_lu_balasubramanian_krayer_ruzie_et al._2010, title={Stable Synthetic Cationic Bacteriochlorins as Selective Antimicrobial Photosensitizers}, volume={54}, ISSN={["1098-6596"]}, DOI={10.1128/aac.00125-10}, abstractNote={Photodynamic inactivation is a rapidly developing antimicrobial treatment that employs a nontoxic photoactivatable dye or photosensitizer in combination with harmless visible light to generate reactive oxygen species that are toxic to cells. Tetrapyrroles (e.g., porphyrins, chlorins, bacteriochlorins) are a class of photosensitizers that exhibit promising characteristics to serve as broad-spectrum antimicrobials. In order to bind to and efficiently penetrate into all classes of microbial cells, tetrapyrroles should have structures that contain (i) one or more cationic charge(s) or (ii) a basic group. In this report, we investigate the use of new stable synthetic bacteriochlorins that have a strong absorption band in the range 720 to 740 nm, which is in the near-infrared spectral region. Four bacteriochlorins with 2, 4, or 6 quaternized ammonium groups or 2 basic amine groups were compared for light-mediated killing against a gram-positive bacterium (Staphylococcus aureus), a gram-negative bacterium (Escherichia coli), and a dimorphic fungal yeast (Candida albicans). Selectivity was assessed by determining phototoxicity against human HeLa cancer cells under the same conditions. All four compounds were highly active (6 logs of killing at 1 microM or less) against S. aureus and showed selectivity for bacteria over human cells. Increasing the cationic charge increased activity against E. coli. Only the compound with basic groups was highly active against C. albicans. Supporting photochemical and theoretical characterization studies indicate that (i) the four bacteriochlorins have comparable photophysical features in homogeneous solution and (ii) the anticipated redox characteristics do not correlate with cell-killing ability. These results support the interpretation that the disparate biological activities observed stem from cellular binding and localization effects rather than intrinsic electronic properties. These findings further establish cationic bacteriochlorins as extremely active and selective near-infrared activated antimicrobial photosensitizers, and the results provide fundamental information on structure-activity relationships for antimicrobial photosensitizers.}, number={9}, journal={ANTIMICROBIAL AGENTS AND CHEMOTHERAPY}, author={Huang, Liyi and Huang, Ying-Ying and Mroz, Pawel and Tegos, George P. and Zhiyentayev, Timur and Sharma, Sulbha K. and Lu, Zongshun and Balasubramanian, Thiagarajan and Krayer, Michael and Ruzie, Christian and et al.}, year={2010}, month={Sep}, pages={3834–3841} }
 @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 ( H 2 BC-Br 3 Br 13 ) . 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. H 2 C-Br 3 M 10 Br 13 ). 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 H 2 BC-Br 3 Br 13 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} }
 @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} }
 @misc{moorman_scannell_balasubramanian_outcalt_leung_2008, title={Synthesis of 2-aralkyloxyadenosines, 2-alkoxyadenosines, and their analogs}, volume={7,342,003}, number={2008 Mar. 11}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Moorman, A. R. and Scannell, M. and Balasubramanian, T. and Outcalt, R. and Leung, E.}, year={2008} }
 @article{ruzie_krayer_balasubramanian_lindsey_2008, title={Tailoring a bacteriochlorin building block with cationic, amphipathic, or lipophilic substituents}, volume={73}, ISSN={["1520-6904"]}, DOI={10.1021/jo800736c}, abstractNote={Bacteriochlorins are attractive candidates for photodynamic therapy (PDT) of diverse medical indications owing to their strong absorption in the near-infrared (NIR) region, but their use has been stymied by lack of access to stable, synthetically malleable molecules. To overcome these limitations, a synthetic free base 3,13-dibromobacteriochlorin (BC-Br3Br13) has been exploited as a building block in the synthesis of diverse bacteriochlorins via Pd-mediated coupling reactions (Sonogashira, Suzuki, and reductive carbonylation). Each bacteriochlorin is stable to adventitious dehydrogenation by virtue of the presence of a geminal dimethyl group in each pyrroline ring. The target bacteriochlorins bear cationic, lipophilic, or amphipathic substituents at the 3- and 13- (β-pyrrolic) positions. A dicarboxybacteriochlorin was converted to amide derivatives via the intermediate diacid chloride. A diformylbacteriochlorin was subjected to reductive amination to give aminomethyl derivatives. A set of 3,5-disubstituted aryl groups bearing lipophilic or amphipathic groups was introduced via Suzuki coupling. Altogether 22 free base bacteriochlorins have been prepared. Eight aminoalkylbacteriochlorins were quaternized with methyl iodide at two or four amine sites per molecule, which resulted in water solubility. Each bacteriochlorin exhibits a Qy absorption band in the range of 720−772 nm. The ability to introduce a wide variety of peripheral functional groups makes these bacteriochlorins attractive candidates for diverse applications in photomedicine including PDT in the NIR region.}, number={15}, journal={JOURNAL OF ORGANIC CHEMISTRY}, author={Ruzie, Christian and Krayer, Michael and Balasubramanian, Thiagarajan and Lindsey, Jonathan S.}, year={2008}, month={Aug}, pages={5806–5820} }
 @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} }
 @misc{alla_choi_dhanoa_difranco_krokhina_li_balasubramanian_zhang_2004, title={Amino acid derivatives}, volume={6,809,207}, number={2004 Oct. 26}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Alla, S. and Choi, S. Y. and Dhanoa, D. and DiFranco, E and Krokhina, G. and Li, K. and Balasubramanian, T. and Zhang, W. C.}, year={2004} }
 @misc{lindsey_balasubramanian_2003, title={Trans beta substituted chlorins and methods of making and using the same}, volume={6,559,374}, number={2003 May 6}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Lindsey, J. S. and Balasubramanian, T.}, year={2003} }
 @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 ∼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 CH3CN 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 CH3CN 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{balasubramanian_strachan_boyle_lindsey_2000, title={Rational synthesis of beta-substituted chlorin building blocks}, volume={65}, ISSN={["0022-3263"]}, DOI={10.1021/jo000913b}, abstractNote={Chlorins bearing synthetic handles at specific sites about the perimeter of the macrocycle constitute valuable building blocks. We previously developed methodology for preparing meso-substituted chlorin building blocks and now present methodology for preparing several complementary β-substituted chlorin building blocks. The chlorins bear one or two β substituents, one meso substituent, a geminal dimethyl group to lock in the chlorin hydrogenation level, and no flanking meso and β substituents. The synthesis involves convergent joining of an Eastern half and a Western half. New routes have been developed to two β-substituted bromo-dipyrromethane monocarbinols (Eastern halves). A new β-substituted Western half was prepared following the method for preparing an unsubstituted Western half (3,3-dimethyl-2,3-dihydrodipyrrin). Chlorin formation is achieved by a two-flask process of acid-catalyzed condensation followed by metal-mediated oxidative cyclization. β-Substituted chlorins have been prepared in 18−24% yield bearing a 4-iodophenyl group at the 8-position, a 4-iodophenyl group or a 4-[2-(trimethylsilyl)ethynyl]phenyl group at the 12-position, and a 4-iodophenyl group and a 4-[2-(trimethylsilyl)ethynyl]phenyl group at diametrically opposed β-positions (2, 12). The latter building block makes possible the stepwise construction of linear multi-chlorin architectures. The chlorins exhibit typical absorption and fluorescence spectra. A systematic shift in the absorption maximum (637−655 nm for the free base chlorins, 606−628 nm for the zinc chlorins) and intensity of the chlorin Qy band (ε up to 79 000 M-1 cm-1) is observed depending on the location of the substituents. The characteristic spectral features and location of substituents in defined positions make these chlorins well suited for a variety of applications in biomimetic and materials chemistry.}, number={23}, journal={JOURNAL OF ORGANIC CHEMISTRY}, author={Balasubramanian, T and Strachan, JP and Boyle, PD and Lindsey, JS}, year={2000}, month={Nov}, pages={7919–7929} }
 @article{strachan_df o'shea_balasubramanian_lindsey_2000, title={Rational synthesis of meso-substituted chlorin building blocks}, volume={65}, ISSN={["1520-6904"]}, DOI={10.1021/jo991942t}, abstractNote={Chlorins provide the basis for plant photosynthesis, but synthetic model systems have generally employed porphyrins as surrogates due to the unavailability of suitable chlorin building blocks. We have adapted a route pioneered by Battersby to gain access to chlorins that bear two meso substituents, a geminal dimethyl group to lock in the chlorin hydrogenation level, and no flanking meso and β substituents. The synthesis involves convergent joining of an Eastern half and a Western half. A 3,3-dimethyl-2,3-dihydrodipyrrin (Western half) was synthesized in four steps from pyrrole-2-carboxaldehyde. A bromodipyrromethane carbinol (Eastern half) was prepared by sequential acylation and bromination of a 5-substituted dipyrromethane followed by reduction. Chlorin formation is achieved by a two-flask process of acid-catalyzed condensation followed by metal-mediated oxidative cyclization. The latter reaction has heretofore been performed with copper templates. Investigation of conditions for this multistep process led to copper-free conditions (zinc acetate, AgIO3, and piperidine in toluene at 80 °C for 2 h). The zinc chlorin was obtained in yields of ∼10% and could be easily demetalated to give the corresponding free base chlorin. The synthetic process is compatible with a range of meso substituents (p-tolyl, mesityl, pentafluorophenyl, 4-[2-(trimethylsilyl)ethynyl]phenyl, 4-iodophenyl). Altogether four free base and four zinc chlorins have been prepared. The chlorins exhibit typical absorption spectra, fluorescence spectra, and fluorescence quantum yields. The ease of synthetic access, presence of appropriate substituents, and characteristic spectral features make these types of chlorins well suited for incorporation in synthetic model systems.}, number={10}, journal={JOURNAL OF ORGANIC CHEMISTRY}, author={Strachan, JP and DF O'Shea and Balasubramanian, T and Lindsey, JS}, year={2000}, month={May}, pages={3160–3172} }
 @article{lammi_ambroise_balasubramanian_wagner_bocian_holten_lindsey_2000, title={Structural control of photoinduced energy transfer between adjacent and distant sites in multiporphyrin arrays}, volume={122}, ISSN={["0002-7863"]}, DOI={10.1021/ja001031x}, abstractNote={A family of diphenylethyne-linked porphyrin dimers and trimers has been prepared via a building block approach for studies of energy-transfer processes. The dimers contain Mg and Zn porphyrins (MgZnU); the trimers contain an additional free base porphyrin (MgZnFbU). In both the dimers and trimers, sites of attachment to the Mg porphyrin (at the meso- or β-position) and diphenylethyne linker (at the para- or meta-positions) were varied, producing four Mg porphyrin−Zn porphyrin arrangements with the following linker configurations: meso-p/p-meso, meso-m/p-meso, β-p/p-meso, and β-m/p-meso. All four trimers employ a meso-p/p-meso Zn porphyrin−Fb porphyrin connection. The ground- and excited-state properties of the porphyrin dimers and trimers have been examined using static and time-resolved optical techniques. The rate of energy transfer from the photoexcited Zn porphyrin to the Mg porphyrin decreases according to the following trend: meso-p/p-meso (9 ps)-1 > β-p/p-meso (14 ps)-1 > meso-m/p-meso (19 ps)-1 > β-m/p-meso (27 ps)-1. In each compound, energy transfer between adjacent porphyrins occurs through a linker-mediated through-bond process. The rate of energy transfer between Zn and Fb porphyrins is constant in each trimer ((24 ps)-1). Energy transfer from the photoexcited Zn porphyrin branches to the adjacent Fb and Mg porphyrins, with nearly one-half to three-fourths proceeding to the Mg porphyrin (depending on the linker). Energy transfer from the excited Mg porphyrin to the nonadjacent Fb porphyrin occurs more slowly, with a rate that follows the same trend in linker architecture and porphyrin connection site: meso-p/p-meso (173 ps)-1 > β-p/p-meso (225 ps)-1 > meso-m/p-meso (320 ps)-1 > β-m/p-meso (385 ps)-1. The rate of transfer between nonadjacent Mg and Fb porphyrins does not change significantly with temperature, indicating a superexchange mechanism utilizing orbitals/states on the intervening Zn porphyrin. Energy transfer between nonadjacent sites may prove useful in directing energy flow in multiporphyrin arrays and related molecular photonic devices.}, number={31}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Lammi, RK and Ambroise, A and Balasubramanian, T and Wagner, RW and Bocian, DF and Holten, D and Lindsey, JS}, year={2000}, month={Aug}, pages={7579–7591} }
 @article{yang_seth_balasubramanian_kim_lindsey_holten_bocian_1999, title={Interplay of orbital tuning and linker location in controlling electronic communication in porphyrin arrays}, volume={121}, ISSN={["0002-7863"]}, DOI={10.1021/ja9842060}, abstractNote={The β-diphenylethyne-linked porphyrin dimers ZnFbU-β (nonlinking meso-mesityl substituents) and F30ZnFbU-β (nonlinking meso-pentafluorophenyl substituents) and their bis-Zn analogues have been examined by static spectroscopic (absorption, fluorescence, electron paramagnetic resonance), time-resolved spectroscopic (absorption, fluorescence), and electrochemical (cyclic and square-wave voltammetry, coulometry) methods. The β-linked dimers were examined to test the hypothesis that the nature of the porphyrin HOMO (a1u versus a2u) in concert with the position of the linker (β-pyrrole or meso carbon) mediates electronic communication (excited-state energy transfer, ground-state hole-hopping). The major findings are as follows: (1) The rate of energy transfer is (56 ps)-1 for ZnFbU-β and (24 ps)-1 for F30ZnFbU-β. (2) The rate of hole/electron hopping in the monooxidized bis-Zn complex [F30Zn2U-β]+ is in the fast-exchange limit and is at least comparable to that for [Zn2U-β]+. These findings indicate that the presence of pentafluorophenyl groups causes enhancement of electronic communication in the β-linked dimers but attenuation in the meso-linked dimers. These opposite effects in the β- versus meso-linked dimers are explained by the fact that both pentafluorophenyl-substituted dimers have a1u HOMOs, which exhibit significant β-pyrrole electron density, whereas both mesityl-substituted dimers have a2u HOMOs, which exhibit large meso-carbon density. Thus, the combination of an a1u HOMO with a β-linker or an a2u HOMO with a meso linker results in optimal electronic communication. Collectively, these results demonstrate that the nature of the frontier orbitals and position of connection of a covalent linker (in addition to distance, orientation, and energetics) must be considered in the design architecture of molecular photonic devices.}, number={16}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Yang, SI and Seth, J and Balasubramanian, T and Kim, D and Lindsey, JS and Holten, D and Bocian, DF}, year={1999}, month={Apr}, pages={4008–4018} }
 @article{balasubramanian_lindsey_1999, title={Synthesis of beta-substituted porphyrin building blocks and conversion to diphenylethyne-linked porphyrin dimers}, volume={55}, ISSN={["0040-4020"]}, DOI={10.1016/S0040-4020(99)00339-7}, abstractNote={A recent hypothesis concerning effects of orbital ordering on electronic communication (excited-state energy transfer, ground-state hole-hopping) in covalently linked porphyrin arrays prompted the development and application of methodology for the synthesis of β-linked porphyrin dimers. Reaction of a β-substituted pyrrole with 2-hydroxymethylpyrrole led to the dipyrromethane bearing a single β-substituent and no meso- nor α-substituents. Condensation of the β-substituted dipyrromethane with an aldehyde and a meso-substituted dipyrromethane gave the desired β-substituted porphyrin building block, albeit in low yield. Four building blocks were prepared with a p-iodophenyl or p-ethynylphenyl group at one β-position, no substituent at the flanking meso-position, and mesityl or pentafluorophenyl groups at the three non-flanking meso-positions. The porphyrin building blocks were coupled via Pd-mediated reactions, affording diphenylethyne-linked dimers with the linker attached at β-positions. This approach provided access to zinc-free base porphyrin dimers and bis-zinc dimers bearing mesityl or pentafluorophenyl groups at the three non-linking meso-positions. The availability of these dimers and monomeric benchmarks enabled a critical test of the orbital ordering hypothesis. This methodology for preparing porphyrin building blocks bearing a lone, non-hindered β-substituent complements existing methods for preparing meso-substituted porphyrin building blocks. The ability to position the linker at the meso- or β-positions provides a desirable level of versatility for incorporating porphyrinic molecules with an a2u or a1u HOMO in various molecular devices.}, number={22}, journal={TETRAHEDRON}, author={Balasubramanian, T and Lindsey, JS}, year={1999}, month={May}, pages={6771–6784} }