Abstract:

The geometries of bis(salicylaldiminatio) Schiff base compounds and their Ni(Ⅱ) complexes were optimized by using ab initio HF method at the 6.31G(d) basis set. On the basis of the stable structures, the electronic spectra of these systems were studied by INDO/CI method. The nonlinear optical(NLO)coefficients were calculated by ZINDO/SOS method. The results show that the hyperpolarizabilities(β and γ) were increased with the increase of the conjugated range. The β and γ values of compound 1 are 35.54×10-30 esu and -1.20×10-34 esu, respectively, but β and γ values of compound 4 in which the conjugated bridge is naphthyl ring are 5422×10-30 esu and -2.00×10-34 esu, respectively. Compound 5 in which the phenyl ring is introduced from the terminal has the largest NLO coefficient. The value of β increased significantly by introducing Ni(Ⅱ) into the complexes, the β value of complexes are 1.7—10.8 times larger than that of other compounds, the value of γ also increased to a different extent.