Theoretical chemical study on NLO properties of polypyridinopyridine and its derivatives

With quantum chemical PM3/FF method, effects of strucure and substituents - NO2 and -NH2 on nonlinear optical properties of polypyridinopyridine(PPY) w ere discussed. The results showed that the beta and gamma values were -5.54 x 10(-29) esu and -1.544 x 10(-32) esu, respectively. In three stable stru ctures of equal-bond length structure (a), cis-structure (b) and trans-stru cture (c), the beta and gamma values of(a) and (c) is larger than (b). More specially, beta and gamma values of (c) increased promptly as the number o f repeat unit increased. When the number of unit was over four, (c) gave th e biggest beta and gamma. In structures of PPY substituted by NO2 and NH2, the effects of pull-push electron and pi -electron delocalization became st ronger, beta increased effectively to about 1.6 x 10(-27) esu. PPY is a pro mising candidate of nonlinear optical (NLO) materials.