Ishida Masatoshi, Furuyama Taniyuki, Lim Jong Min, Lee Sangsu, Zhang Zhan, Ghosh Sudip K, Lynch Vincent M, Lee Chang-Hee, Kobayashi Nagao, Kim Dongho, Sessler Jonathan L
Department of Chemistry, Yonsei University, Seoul, 03722, Korea.
Department of Chemistry and Biochemistry, Graduate School of Engineering, and Center for Molecular Systems, Kyushu University, Fukuoka, 819-0395, Japan.
Chemistry. 2017 May 11;23(27):6682-6692. doi: 10.1002/chem.201700759. Epub 2017 Apr 20.
Detailed electronic, structural, photophysical, and redox studies of a series of meso-pentafluorophenyl-substituted hexaphyrins, namely amethyrin (1), rosarin (2), and rubyrin (3), are described. In prior work, it was found that the electronic states of the antiaromatic hexapyrrolic macrocycle, [24]rosarin 2, could be modified by exposure to several Brønsted acids (e.g., HCl, HBr and HI) to produce either one- and two-electron reduced species, or both. In an effort to gain further insights into the reactivity of hexaphyrins possessing different π-conjugation pathways, the β-dodecamethyl-substituted [24]amethyrin 1 was prepared and its electronic structure was analyzed along with that of the o-phenylene-bridged [26]rubyrin 3 and rosarin 2 The [4n] and [4n+2] π-conjugated formulations of 2 and 3, respectively, were inferred from steady-state, fs-transient absorption and two photon absorption measurements. Similar photophysical analyses lead to the conclusion that 1 is best considered as nonaromatic or weakly antiaromatic. Magnetic circular dichroism (MCD) spectroscopic analyses of hexaphyrins 1 and 3, as well as comparisons to 2, and theoretical perimeter MO diagram analyses provided support for the electronic assignments. In contrast to what was found for 2, simple protonation of 1 and 3 by halohydric acids did not induce an evident, redox-based change in the electronic structure of the macrocycle.
本文描述了一系列中位五氟苯基取代的六卟啉，即紫红素（1）、玫瑰红素（2）和红宝石红素（3）的详细电子、结构、光物理和氧化还原研究。在之前的工作中，发现反芳香性六吡咯大环[24]玫瑰红素2的电子态可通过暴露于几种布朗斯特酸（如HCl、HBr和HI）进行修饰，以产生单电子和双电子还原物种，或两者皆有。为了进一步深入了解具有不同π共轭途径的六卟啉的反应性，制备了β-十二甲基取代的[24]紫红素1，并将其电子结构与邻亚苯基桥连的[26]红宝石红素3和玫瑰红素2的电子结构进行了分析。通过稳态、飞秒瞬态吸收和双光子吸收测量分别推断出2和3的[4n]和[4n+2]π共轭形式。类似的光物理分析得出结论，1最好被视为非芳香性或弱反芳香性。对六卟啉1和3进行磁圆二色性（MCD）光谱分析，并与2进行比较，以及理论周边分子轨道图分析为电子归属提供了支持。与2的情况相反，卤代氢酸对1和3的简单质子化并未在大环的电子结构中引起基于氧化还原的明显变化。
