Three SN Schiff base ligands derived from dithiocarbazate were prepared. Their neutral bisligand chelates, ML2^1^～^3 [M=Ni(II), Cu (II), Pd(II) and Pt(II)], forming D-M-D and A-M-A type complexes were also prepared and characterized (D=donor, M=metal A=acceptor). Magnetic and spectroscopic data suggest a square-planar structure for the complexes. ESR spectra and variable-temperature magnetic susceptibility data supported a square-planar structure of Cu(II) chelate too. Single crystal X-ray diffraction analysis of the copper (II) chelate established that the Schiff base ligand lost a proton from its tautomeric thiol form and coordinated to metal via the mercapto sulfur and β-nitrogen. The geometry around Cu(II) is square- planar with two equivalent Cu-N and Cu-S bonds, forming an electronic delocalization system. The third-order NLO properties of them were also studied. The results show that the electro-donation group is quite helpful for the complexes exhibit higher third-order response.

Key words: METHANETHIOIC ACID P, CRYSTAL STRUCTURE OF COMPLEX, NON LINEAR OPTIC CRYSTAL, NICKEL COMPLEX, COPPER COMPLEX, PALLADIUM COMPLEX, PLATINUM COMPLEX