Theoretical and experimental study of the second-order polarizabilities of Schiff's bases for nonlinear optical applications

A series of twenty-four Schiff's bases was synthesized and nonresonant static molecular second order polarizabilities (beta) of these compounds were theoretically calculated and compared with experimental values. The computational method employed obtained: (a) values of polarization Versus static electric fields using a semiempirical Hamiltonian; (b) all tensor elements of beta by performing polynomial fits of the former data, within the finite-field approach. The experimental values were obtained using a modified electric field induced second harmonic generation (EFISH) experiment with 1,4-dioxane as the solvent. The measured quantities were the projection of beta on mu (the permanent dipole moment), relative to MNA (2-methyl-4-nitroaniline). The correlation between the predicted static molecular quantities and their corresponding experimental Values was 0.95 (based on a simple least-squares regression forced through the origin). A factor of 8.7 +/- 0.3 was determined to be the adjustment parameter for Schiff's bases to account for the solvent and dispersion effects at the fundamental wavelength of 1064 nm. (C) 1997 Elsevier Science B.V.