Department of Chemistry and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, PO Box 56, Dunedin, New Zealand.
Spectrochim Acta A Mol Biomol Spectrosc. 2009 Nov;74(4):931-5. doi: 10.1016/j.saa.2009.08.040. Epub 2009 Aug 25.
Zinc meso-tetraphenylporphyrin (ZnTPP) was modified in such a way to allow the effect of an asymmetric structural distortion on its optical properties to be investigated. This involved the fusion of a phenyl group to an adjacent pyrrole ring via a carbonyl bridge. With the aid of Density Functional Theory (DFT) and time-dependent DFT (TD-DFT) calculations it was found that the asymmetric distortion away from planarity induced by the carbonyl fusion resulted in a loss of degeneracy in the two lowest unoccupied molecular orbitals (LUMOs). The effect was a red shift of the electronic absorbance bands, an increased Q:B ratio from 0.046 in ZnTPP to 0.096 in the fused derivative, and the appearance of additional UV-vis peaks. This study therefore suggests that structural distortions, as well as electronic substituents may be used to alter absorbance spectra, a technique which is of interest in the design of light-harvesting dyes.
锌原卟啉（ZnTPP）经过修饰，以研究不对称结构变形对其光学性质的影响。这涉及通过羰基桥将一个苯基融合到相邻的吡咯环上。借助密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）计算，发现羰基融合引起的离平面不对称变形导致两个最低未占据分子轨道（LUMO）的简并性丧失。这种影响导致电子吸收带的红移，在融合衍生物中，Q:B 比从 ZnTPP 的 0.046 增加到 0.096，并且出现了额外的紫外可见峰。因此，这项研究表明，结构变形以及电子取代基可用于改变吸收光谱，这种技术在设计光捕获染料方面具有重要意义。
