Rhoda Hannah M, Akhigbe Joshua, Ogikubo Junichi, Sabin Jared R, Ziegler Christopher J, Brückner Christian, Nemykin Victor N
Department of Chemistry & Biochemistry, University of Minnesota Duluth , Duluth, Minnesota 55812, United States.
Department of Chemistry, University of Connecticut , Unit 3060, Storrs, Connecticut 06269-3060, United States.
J Phys Chem A. 2016 Jul 28;120(29):5805-15. doi: 10.1021/acs.jpca.6b04618. Epub 2016 Jul 19.
A large set of free-base and transition-metal 5,10,15,20-tetraphenyl-substituted chlorins, bacteriochlorins, and isobacteriochlorins and their pyrrole-modified analogues were investigated by combined UV-visible spectroscopy, magnetic circular dichroism (MCD), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches and their spectral characteristics were compared to those of the parent compounds, free-base tetraphenylporphyrin 1H2 and chlorin 2H2. It was shown that the nature of the pyrroline substituents in the chlorin derivatives dictates their specific UV-vis and MCD spectroscopic signatures. In all hydroporphyrin-like cases, MCD spectroscopy suggests that the ΔHOMO is smaller than the ΔLUMO for the macrocycle-centered frontier molecular orbitals. DFT and TDDFT calculations were able to explain the large broadening of the UV-vis and MCD spectra of the chlorin diones and their derivatives compared to the other hydroporphyrins and hydroporphyrin analogues. This study contributes to the further understanding of the electronic effects of replacing a pyrrole in porphyrins by pyrrolines or other five-membered heterocycles (oxazoles and imidazoles).
通过紫外可见光谱、磁圆二色性（MCD）、密度泛函理论（DFT）和含时密度泛函理论（TDDFT）相结合的方法，对一大组游离碱和过渡金属的5,10,15,20-四苯基取代二氢卟吩、细菌叶绿素和异细菌叶绿素及其吡咯修饰类似物进行了研究，并将它们的光谱特征与母体化合物游离碱四苯基卟啉1H2和二氢卟吩2H2的光谱特征进行了比较。结果表明，二氢卟吩衍生物中吡咯啉取代基的性质决定了它们特定的紫外可见光谱和MCD光谱特征。在所有类氢化卟啉的情况下，MCD光谱表明，以大环为中心的前沿分子轨道的ΔHOMO小于ΔLUMO。与其他氢化卟啉和氢化卟啉类似物相比，DFT和TDDFT计算能够解释二氢卟吩二酮及其衍生物的紫外可见光谱和MCD光谱的大幅展宽。这项研究有助于进一步理解用吡咯啉或其他五元杂环（恶唑和咪唑）取代卟啉中的吡咯所产生的电子效应。
