CRYSTAL-STRUCTURE AND 3RD-ORDER NONLINEARITY OF NICKEL(II) AND COPPER(II) COMPLEXES WITH S-METHYL BETA-N-(4-NITROBENZAL)METHYLENEDITHIOCARBAZATE

Ni-II and Cu-II complexes of general formula ML2 [HL = S-methyl-beta-N -(nitrobenzal)methylene- dithiocarbazate] have been synthesized and ch aracterized. The Schiff base acts as a single, negatively charged bide ntate ligand forming extensive electron delocalization system. Single crystal X-ray diffraction analysis of the copper(II) complex revealed that the ligand lost a proton from its tautomeric thiol form and coord inates to Cu-II via mercapto sulfur and beta-nitrogen atoms. The geome try of the Cu-II ion is square-planar with two equivalent Cu--S and Cu --N bonds. The two nitrobenzal rings and the coordinated moieties are almost in one plane, forming an electronic delocalization system. Thir d-order response-determinations show that the extensive electron deloc alization is quite helpful for the complexes exhibit higher second ord er molecular hyperpolarizability. Crystal structure of the free ligand is also determined for comparison. (C) 1997 Elsevier Science Ltd.