新型双重电荷转移分子的二阶非线性光学性质的 理论研究

以INDO/SCI方法为基础，按完全态求和(SOS)公式编制了计算分子二阶非线性光学系数β~i~j~k和β~μ的程序。研究了1,2-二氨基-4,5-二硝基苯1和其异构体1,3-二氨基-4,6-二硝基苯2的电子光谱和二阶非线性光学性质。计算表明分子1具有与分子2几乎相等的二阶非线性极化率。但由于分子1的偶极矩明显大于分子2的，故分子1的μβ值比分子2的μβ值大的多。在此基础上，研究了2,3-二(β-苯乙烯基)-5,6-二氰基吡嗪和2,3-二(β-噻吩乙烯基)-5,6-二氰基吡嗪和2,3-二(β-噻吩乙烯基)-5,6二氰基吡嗪衍生物的电子光谱和二阶非线性光学性质。结果表明，这些化合物均具有两个相距很近的强吸收峰，它们对β值的呈加和模式。由于这类化合物特征吸收峰均位于413nm以下且具有大的μβ值，所以，它们是一类很有前途的二阶非线性光学候选材料。

Theoretical study on second-order nonlinear optical properties of a new type of multicharge-transfer chromophores

On the basis of INDO-SCI program, we have designed a program to calculate the nonlinear second-order polarizability β~i~j~k and β~μ according to the SOS expression. The electronic spectra and second- order nonlinear optical properties of 1,2-diamino-4,5-dinitrobezene 1 and 1,3-diamino-4,5-dinitrobezene 2 were studied. The calculated results indicate that molecule 1 possesses second-order nonlinear optical polarizability comparable to that of molecule 2. Because the dipole moment of 1 is much larger than that of 2, so the value of μβ of 1 is much larger than that of 2. Based on the studied above, the electronic spectra and second-order nonlinear optical properties of 2,3-bis(β-phenylethenyl0-5,6-dicyanopyrazine and 2,3-bis(β- thienylethenyl)-5,6-dicyanopyrazine derivatives were studied as well. It is found that all these compounds possess two low-lying excited electronic states that are very close to each other in energies, both contributing to the second-order nonlinear optical polarizability in an additive fashion. These derivatives are good candidates as chromophores due to their absorption <413 nm and large μβ values.