Synthesis and Characterization of New Nickel(II) and Zinc(II) Schiff Base Complexes Containing Disulfide Bond

Schiff base complexes are compounds that contain the azomethine group (–CH=N–) in their structure which are generally synthesized by the condensation of primary amines and active carbonyl groups. The interest of studying Schiff base complexes containing different donor atoms such as ONS arise from their significant antifungal, antibacterial and anticancer activities [1]. In addition, the presence of both hard and soft donor groups in one compound increases the coordination ability towards hard as well as soft acidic metals. Also, the chelating properties of Schiff base ligands in their complexes display manifold applications in medicine, industry and agriculture [2]. Schiff base complexes recently have taken more attention in bioinorganic, biochemistry and medicine because of the fact that they have antimicrobial and chemotherapy features [3]. The biological activity potential of complexes containing sulfur and nitrogen may be the reason for this increased interest. In this work, two new complexes of nickel(II) and zinc(II) were synthesized by the reaction of NiCl2.6H2O and ZnCl2.H2O with two moles of bidentate Schiff base ligand in ethanol at 58 ̊C. In these complexes NSO atoms were observed but Schiff base was coordinated as a bidentate ligand through NO donor atoms of phenolic and azomethine groups in metal complexes and the thiolic groups were oxidized and formed disulfide bond. The metal centers were coordinated to all the available functional groups on the double Schiff base ligand. These new complexes were characterized by the spectroscopic techniques such as UV–Vis spectroscopy, FT-IR, 1H NMR and conductometry.