基于密度泛函理论的叶绿素A性质的研究
Study on the nature of chlorophyll A based on density functional theory

在液相环境中，采用密度泛函理论（DFT）、含时密度泛函理论（TD-DFT）、Multiwfn波函数分析软件，在pbepbe/6-311g(d)基组水平上，计算并分析了Chlorophyll a的结构、紫外光谱和电子―空穴分布，结果表明：pbepbe/6-311g(d)方法是计算Chlorophyll a紫外吸收光谱更精确的方法；Chlorophyll a分子吡咯环与取代基相互作用的过程中，吡咯环Ⅳ受侧链“尾巴”的影响最大；理论计算的紫外光谱与实验数据吻合较好，其中635.71nm和446.87nm处的两个吸收峰可认为是Chlorophyll a的特征吸收峰；侧链或取代基团在Chlorophyll a激发过程中是给电子体，卟啉“头”既是供电子体，也是电子受体。
In the process of photosynthesis, most chlorophyll a plays the key role of the absorption and transition of light, and it has the function of transforming light energy in a few special conditions. In order to deeply explore the mechanism of photosynthesis of chlorophyll a, three quantum chemistry tools including the density functional theory (DFT), time-dependent density functional theory (TD-DFT) and Multiwfn wave function analysis software package at the level of pbepbe/6-311g(d) are used to calculate and analyze the structure, ultraviolet spectra and electron-hole distribution of chlorophyll a in the liquid phase environment in this paper. The results showed that the pbepbe/6-311g (d) method is the more accurate method to calculate ultraviolet absorption spectrum of chlorophyll a. The side chains "tail" has been the biggest influence on pyrrole ring Ⅳin the process of interaction between pyrrole ring of chlorophyll a and substituent. The UV spectra calculated by the theory are in good agreement with the experimental data, in which the two absorption peaks of 635.71nm and 446.87nm can be considered as the characteristic absorption peaks of Chlorophyll a. The side chain groups or substituent group is electron donor in the excitation process of Chlorophyll a, and porphyrin "head" is not only the electron donor, but also the electron acceptor. The results of this study have some guiding significance for understanding the mechanism of photosynthesis.