中文摘要：

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,计算并分析了叶绿素A的结构、紫外光谱和电子—空穴分布,结果表明：pbepbe/6-311g（d）方法是计算叶绿素A紫外吸收光谱更精确的方法;叶绿素A分子的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635.71 nm和446.87 nm处的两个吸收峰可认为是叶绿素A的特征吸收峰;侧链或取代基团在叶绿素A激发过程中是给电子体,卟啉“头”既是电子供体,也是电子受体.

英文摘要：

In order to deeply explore the mechanism of photosynthesis of chlorophyll a, three quantum chemistry tools including the density functional theory （DFF） , time -dependent density functional theory （TD - DFF） and Muhiwfn wave function analysis software package at the level of pbepbe/6 -31 l g（d） are used to calculate and analyze the structure, ultraviolet spectra and electron - hole distribution of chlorophyll a in the liquid phase envi- ronment in this paper. The results showed that the pbepbe/6 -311 g （d） method is the more accurate method to calculate ultraviolet absorption spectrum of chlorophyll a. The side chains ＂tail＂ has the biggest influence on pyrrole ring IV in 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 635.71 nm and 446.87 nm can be considered as the characteristic absorption peaks of chlorophyll a. The side chain group 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.