THEORETICAL AND EXPERIMENTAL-STUDY OF THE 2ND-ORDER POLARIZABILITIES OF SCHIFF 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 compou nds were theoretically calculated and compared with experimental value s. The computational method employed obtained: (a) values of polarizat ion Versus static electric fields using a semiempirical Hamiltonian; ( b) all tensor elements of beta by performing polynomial fits of the fo rmer data, within the finite-field approach. The experimental values w ere obtained using a modified electric field induced second harmonic g eneration (EFISH) experiment with 1,4-dioxane as the solvent. The meas ured quantities were the projection of beta on mu (the permanent dipol e moment), relative to MNA (2-methyl-4-nitroaniline). The correlation between the predicted static molecular quantities and their correspond ing experimental Values was 0.95 (based on a simple least-squares regr ession forced through the origin). A factor of 8.7 +/- 0.3 was determi ned to be the adjustment parameter for Schiff's bases to account for t he solvent and dispersion effects at the fundamental wavelength of 106 4 nm. (C) 1997 Elsevier Science B.V.