Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, P.R. China.
J Am Chem Soc. 2014 Jul 9;136(27):9598-607. doi: 10.1021/ja502729x. Epub 2014 Jun 24.
Porphodilactones represent the porphyrin analogues, in which the peripheral bonds of two pyrrole rings are replaced by lactone moieties. They provide an opportunity to investigate how β-substituent orientation of porphyrinoids modulates the electronic structures and optical properties, in a manner similar to what is observed with naturally occurring chlorophylls. In this work, a comprehensive description of the synthesis, characterization, and optical properties of meso-tetrakispentafluorophenylporphodilactone isomers is first reported. The β-dilactone moieties are found to lie at opposite pyrrole positions (trans- and cis-configurations are defined by the relative orientations of the carbonyl group when one lactone moiety is fixed), in accordance with earlier computational predictions (Gouterman, M. J. Am. Chem. Soc. 1989, 111, 3702). The relative orientation of the β-dilactone moieties has a significant influence on the electronic structures and photophysical properties. For example, the Qy band of trans-porphodilactone is red-shifted by 19 nm relative to that of the cis-isomer, and there is a 2-fold increase in the absorption intensity, which resembles the similar trends that have been reported for natural chlorophyll f and d. An in depth analysis of magnetic circular dichroism spectral data and TD-DFT calculations at the B3LYP/6-31G(d) level of theory demonstrates that the trans- and cis-orientations of the dilactone moieties have a significant effect on the relative energies of the frontier π-molecular orbitals. Importantly, the biological behaviors of the isomers reveal their different photocytotoxicity in NIR region (>650 nm). The influence of the relative orientation of the β-substituents on the optical properties in this context provides new insights into the electronic structures of porphyrinoids which could prove useful during the development of near-infrared absorbing photosensitizers.
卟吩并二酮代表卟啉类似物，其中两个吡咯环的外围键被内酯部分取代。它们提供了一个机会来研究卟啉类似物的β取代基取向如何调节电子结构和光学性质，这与天然存在的叶绿素所观察到的方式相似。在这项工作中，首次全面描述了间四（五氟苯基）卟吩并二酮异构体的合成、表征和光学性质。β-二内酯部分位于相反的吡咯位置（反式和顺式构型通过一个内酯部分固定时羰基的相对取向来定义），这与早期的计算预测一致（Gouterman，M. J. Am. Chem. Soc. 1989, 111, 3702）。β-二内酯部分的相对取向对电子结构和光物理性质有显著影响。例如，反式卟吩并二酮的 Qy 带相对于顺式异构体红移了 19nm，并且吸收强度增加了 2 倍，这类似于天然叶绿素 f 和 d 报道的类似趋势。对磁圆二色光谱数据和 TD-DFT 计算的深入分析表明，内酯部分的反式和顺式取向对前沿π分子轨道的相对能量有显著影响。重要的是，异构体的生物学行为揭示了它们在近红外区域（>650nm）的不同光细胞毒性。这种情况下β取代基相对取向对光学性质的影响为卟啉类似物的电子结构提供了新的见解，这可能对近红外吸收光敏剂的开发有用。
