取代基及共轭链长对共轭多烯二阶线性光学系数影响的量子化学研究

本文采用引入外场微扰的CNDO/S-CI方法, 计算了一系列取代共轭多烯分子的二阶非线性光学系数β~vec, 探讨了 取代基及共轭链长与分子微观非线性光学效应的关系和规律。结构表明:吸电子或供电子基团的引入, 有利于增强分子的微观非线性光学效应, 但该效应随取代基数目增多有减缓的趋势, "饱和"取代时由于"饱和效应"而使β~vec值降低; 取代基间的距离增大, 分子的β~vec值提高, 端基代时β~vec值最大; 取代共轭多烯的lnβ~vec与分子中所含双键数n之间具有线性关系。本文还对上述结论给出了理论解释。

Quantum chemical study on the effect of the substituent and the conjugated length in substituted polyenes for second order nonlinear-optical coefficients

The second order nonlinear-optical coefficients of a series of substituted polyenes have been calculated by the semi-empirical CNDO/S-CI method. The results show that the introduction of the electronic donor or acceptor and the increase in the distance between the substituents and the length of the conjugated chain may enhance nonlinear optical response. It is also shown that the calculated In bvec is linear with the no. of double bonds in planar and linear trans-polyenes. A saturation effect in substitution is discovered. The theor. explanations are presented for these results. Based on the above discussion one can get the guidelines for synthesis of mols. with larger SHG (second harmonic generation) coefficients