具有不同取代基团的香豆素系列分子二阶非线性光学性质的DFT研究

DFT Study on the second-order nonlinear optical properties of coumarin series molecules with various substituents

本文设计了具有不同取代基团的7-苯乙烯基香豆素和4-苯乙烯基香豆素的A、B两个系列共14个化合物分子.采用密度泛函理论B3LYP/6-31G方法对其几何构型进行了全结构优化.在所得优化结构的基础上对这些分子的稳态二阶非线性光学(NLO)系数β值进行计算分析,同时用含时密度泛函理论(TD-DFT)对这些分子的电子性质进行了研究.结果表明:此类香豆素化合物具有较大的分子β值,其中A类分子的共面性好,共轭链长,β值均比B类分子的大.14个化合物中前线分子轨道能级差越小的化合物,其β_(wt)值越大.各分子前线分子轨道跃迁对二阶NLO)效应有明显的贡献.

The objective of this investigation was to design a series of coumarin with various substituents which show high nonlinear optical activity. The full geometry optimisations of designed coumarin systems were performed using Density Functional Theory （DFT） method at B3LYP/6-31G level of theory. The calculations of the static second-order NLO polarizabilities（β） of these systems were performed at the same level of theory. Combined with time-dependent density-functional theory（TD-DFT）, the molecular electric spectrum was calculated. The results indicate that this series of coumarin have high βvalues. And series A have better planarity, longer conjugated bridge and larger βtot value than series B. The energy transition of frontier molecular orbitals is the key factor to the second-order NLO response.