MOLECULAR DESIGN STUDY ON THE NEW ORGANIC NONLINEAR OPTICAL MATERIALS

In this paper,the second-order nolinear-optical coefficients of a series of conjugated substituted polyenes have been colculated by the semi-empirical CNDO/S-CI method.we have studied in deiail the influence on the number of substituents,the location of the substituents and the conjugation length in motecules to the NLO coefficient Bvace The results showed that the introduetion of the electroinc donor and acceptor groups and the increase in the distance between the substituents and the conjugated length may lead to enhanced NLO responses.It is also shown that the caiculoted In Bvec is linear with the number of double bonds in planar and linear tians substituted polyenes.A saturation effect in substitution is also presented.Based on these discussion one can provide the theorilical guidelines for designing and synthesizing of molecules with larger NLO coefficients.

In this paper, the second-order nonlinear-optical coefficients of a series of conjugated substituted polyenes have been calculated by the semi-empirical CNDO/S-CI method, we have studied in detail the influence on the number of substituents, the location of the substituents and the conjugation length in molecules to the NLO coefficient β The results showed that the introduction of the electronic donor and acceptor groups and the increase in the distance between the substituents and the conjugated length may lead to enhanced NLO responses. It is also shown that the calculated ln β_(vec) is linear with the number of double bonds in planar and linear trans substituted polyenes. A saturation effect in substitution is also presented. Based on these discussion one can provide the theoritical guidelines for designing and synthesizing of molecules with larger NLO coefficients.