手性联萘桥联双卟啉的电子光谱与二阶非线性光学性质

在6-31G(d,p)水平上用B3LYP方法对手性联萘桥联双卟啉系列分子进行几何构型优化. 用半经验ZINDO/S方法计算了这些分子的电子光谱, 结果表明手性联萘桥联双卟啉中两个卟啉生色团之间存在强的激子耦合作用, B带的Davydov分裂大小与两个卟啉环的相对取向以及卟啉环中心之间距离有关. 用ZINDO/SOS方法计算了分子的一阶超极化率. 卟啉环上引入推/拉电子基团可以有效地提高手性联萘桥联双卟啉的二阶非线性光学系数. 一阶超极化率的大小与双卟啉中推/拉电子基团的空间排列方式有关. 一阶超极化率的提高不仅与分子激发态与基态偶极矩差增大有关, 还和基态偶极矩与激子耦合激发态跃迁矩矢量的相对取向密切相关.

Electronic Spectra and Second-Order Nonlinear Optical Properties of Binaphthyl Bridged Chiral Bis-Porphyrins

The geometries of a series of binaphthyl bridged chiral bis-porphyrins were optimized using B3LYP method at 6-31G(d,p) basis set level. The electronic spectra of these porphyrins were then calculated using the semi-empirical ZINDO/S method. Results showed that strong exciton coupling interactions between the two porphyrin chromophores existed in these bis-porphyrins. Davydov splitting of the B bands were related to both the distances and the relative orientations of the two porphyrin rings. First hyperpolarizabilities of these porphyrins were calculated using the ZINDO/SOS method. The second-order nonlinear optical properties of the binaphthyl bridged chiral bis-porphyrins were greatly improved by introducing push/pull substituents onto the porphyrin chromophore. The first hyperpolarizabilities of binaphthyl bridged chiral bis-porphyrins depend on the spatial arrangement of the substituents. The increase in first hyperpolarizabilities of bis-porphyrins is not only related to increasing the dipole moment different between excited and ground state, but also to the relative orientations between the ground state dipole moment vectors and the exciton coupling transition moment vectors.