HIGHLY POLARIZABLE METALLIC COMPLEXES FOR NONLINEAR OPTICS - COBALTOUS COMPLEXES OF UNSYMMETRICAL HYDRAZONE IMINE GLYOXAL DERIVATIVES

The synthesis of 1-(p-phenylhydrazono)-2-(phenylimino)ethane derivatives, unsymmetrically substituted in the para positions with an electron acceptor (-NO2) and an electron donor (-OMe or -NMe2), is described, and the corresponding cobaltous complexes are prepared. X-ray diffraction on a single crystal of the dimethylamino complex has been performed (space group: P1BAR), showing that the coordination site around the cobalt ion is nearly tetrahedral. The complex itself is approximately of C2 symmetry. The inversion center of the space group transforms one optical isomer into the other. The hyperpolarizability coefficients (beta) of the ligands in their cis and trans forms, and those of the neutral cobaltous complexes, have been determined in solution by the electric field induced second harmonic (EFISH) technique. The magnitude of the beta-value obtained for the complex is larger than the value calculated from the tensorial addition of the molecular hyperpolarizability coefficients of the ligands. The importance of the cation on the nonlinear optical properties of metalloorganic complexes is outlined.