SYNTHESIS AND 2ND-ORDER NONLINEAR-OPTICAL PROPERTIES OF NEW COPPER(II), NICKEL(II), AND ZINC(II) SCHIFF-BASE COMPLEXES - TOWARD A ROLE OF INORGANIC CHROMOPHORES FOR 2ND-HARMONIC GENERATION

A new Schiff-base ligand based on the condensation of diaminomaleonitr ile and 4-(diethylamino)salicylaldehyde is reported with its copper, n ickel, and zinc complexes. Their second-order nonlinear optical proper ties are investigated by electric field induced second harmonic (EFISH ) and ZINDO quantum-chemical calculations to probe the role of the met al center in the nonlinearity. All the complexes exhibit a second-orde r nonlinear response that is larger than that of the ligand with an hy perpolarizability (beta) value of 400 (+/-100) 10(-30) cm(5) esu(-1) f or the zinc derivative at 1.34 mu m. Theoretical calculations indicate that the two-level model is inadequate to describe the nonlinearity i n such systems.