对苯二甲酸二苯酯类液晶化合物光谱和二阶非线性光学性质的理论研究

在密度泛函理论B3LYP/6-31G*水平上计算对苯二甲酸二苯酯类液晶化合物分子的几何结构、振动光谱、电子光谱和非线性光学性质, 分析讨论端接基对其光谱与非线性光学性质的影响. 结果表明, 端接基的引入对该类分子的几何结构影响不大. 烷氧基的链长对分子振动光谱的影响很小, 端基引入CN时, C＝O的伸缩振动频率蓝移9 cm^－1. TD-DFT计算表明, 最大吸收光谱源于分子中HOMO→LUMO的p→p*跃迁, 对应的最大吸收波长值在313～375 nm之间, 属于紫外区. 端接强供电子基团可以提高分子的二阶非线性光学性质.

Theoretical Study on Spectra and Second-Order Nonlinear Optical Properties of Liquid Crystal Compound Diphenyl Terephthalates

Theoretical study on diphenyl terephthalate molecules has been carried out at B3LYP/6-31＋G* level to obtain optimized equilibrium structures, vibrational spectra, electronic spectra and nonlinear optical proper-ties. The effects of 4-substituting terminal groups on the spectra and nonlinear optical properties have been discussed. The results show that the introduction of 4-substituting terminal groups has little effect on the structure. The length of alkyl chains has little effect on the vibrational spectra. The introduction of CN makes C＝O stretching vibration frequencies blue-shifted 9 cm^－1. The first excited state electronic transition energy has been calculated using time-dependent density functional theory. The results show that the largest absorption spectra of the title compounds were obtained from the p→p* electron transition from the highest occupied molecular orbital to the lowest unoccupied molecular orbital, and λ_max was obtained in 313～375 nm, belonging to the UV absorption area. The introduction of a strong electron-donor group results in enlarging the second-order nonlinear optical proper-ties.