Abstract: The structures, UV-Vis spectra of 2-phenylbenzothiazole and it′s derivatives has been studied by using the ZINDOmethodology. The calculated UV-Vis spectra are in good agreement with the observed value. On the basis of ZINDOmethods, according to the sum-over-states(SOS) formula, the program for the calculation of nonlinear second order optical susceptibilities β_ijk and β_μ has been devised, and the nonlinear second order optical properties of 2-phenylbenzothiazole and it′s derivatives has been studied by using this methodology. Compared with molecule 1, all of the derivatives have relative large nonlinear second-order optical susceptibilities. The calculation results show that with the increase of the push-pull effects the nonlinear second order optical susceptibilities increased. The electronic donating substituents attached to benzene ring and the electronic withdrawing substituents attached to benzothiazole ring are favourable for increasing the nonlinear second order optical susceptibilities. The structure that the electronic donating substituents attached to 13 position and the electronic withdrawing substituents attached to 6 position has the highest nonlinear second order optical susceptibilities β_μ.

Key words: Phenylbenzothiazole, UV spectrum, Nonlinear second-order optical susceptibility, ZINDO-SOS