A new schiff base derivative (ShBD) [2,2(biphenyl-4-4-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1- ylidene)diphenol] was synthesized, and their structure was characterized by FTIR and CHN. The thin films was prepared by cast method, and the structural investigations performed by means of X-ray diffraction (XRD) technique which showed the shape structure. The dispersion of the refractive index was discussed in terms of the Wemple-DiDomenico single oscillator model. The values of some important parameters of the studied films are determined, such as Eo, Ed, ε∞ and a simple relation is suggested to estimate the third-order optical nonlinear susceptibility χ (3). The estimations of the corresponding χ (3)and ε∞ are (1.02×10-10esu), (4.12) respectively.
