甲氧基苯基偶氮衍生物电子结构与二阶NLO性质的HF/FF方法研究

Theoretical studies on electronic structures and second NLO properties of methoxy phenyl azobenzene derivatives with HF/FF method

采用量子化学HF方法在631G水平上优化6个甲氧基苯基偶氮衍生物分子的几何构型,利用HF/631G*方法计算它们的偶极矩、电荷分布、前线分子轨道能级并结合有限场(FF)方法计算二阶非线性光学系数.结果表明,偶氮苯衍生物分子具有很好的共轭性,在给吸电子基团作用下,电荷转移明显,展现示出较强的极性.偶氮苯衍生物分子与苯乙烯、Schiff碱类衍生物相似,也具有很好二阶非线性光学活性,同时六元杂环取代的偶氮苯衍生物分子二阶非线性光学系数比未取代的大,五元杂环取代结果相反.

The geometric structures of six methoxy phenyl azobenzene derivatives were optimized with HF/6-31G method. The dipole moment, electron population and energy level of frontier molecular orbitals were obtained with HF/6-31G~* method, moreover,the second order nonlinear optical coefficients were calculated combined with FF method. The results indicated that (1) azobenzene derivatives possess good conjugation. When linked with electron-donor and electron-acceptor, the charge transfer is obvious, thus shows strong polarity. (2) azobenzene derivatives has very large second order nonlinear optical properties as well as phenethylene and schiff base derivatives. The second order nonlinear optical coefficients of azobenzene derivates substituted by six heteroatomic rings are higher than that of unsubstituted. However, for five heteroatomic rings substituent,the result is just on the opposite.