On the basis of ZINDO methods using the sum-over-states expression, we have devised the program for the calculation of nonlinear second- order optical susceptibilities β~i~j~k and β~μ of molecules, and studied the structures and nonlinear optical properties of unsymmetric bis(phenylethynyl) benzene series derivatives. The UV- spectrum, μ, β, μβ, β~0, μβ~0, and the charge-transfer of excited state of unsymmetric bis(phenylethynyl) benzene series derivatives were calculated. The influence of the molecular conjugated chain length and the electron-donating group on β~μ was examined. Microscopic explanations for the calculated results are given.

Key words: TOLANE (=DIPHENYLACETYLENE), NON LINEAR OPTICS, CHARGE TRANSFER