Synthesis, Characterization, Enzyme Inhibition and Antioxidant Activity of NickelII Complex of a Schiff Base

Abstract

A novel active NiII complex of the Schiff base ligand ((E)-methyl-6-benzyl-2-(2-hydroxy-3- methoxybenzylideneamino)-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate) has been synthesized. FT-IR, UV-Vis, NMR, microanalysis, mass spectroscopy and physical studies (TGA, molar conductivity, melting point) were used to characterize the newly prepared NiII complex. Various characterization data suggested that the Schiff base ligand, coordinated by the nitrogen atom of the azomethine, the oxygen atom of the carbonyl and the oxygen atom of the hydroxyl group. Then, deprotonation with metal ions in a molar ratio of 1:1, has the general formula [LNiCl(H2O)2]∙H2O. The low molar conductivity values confirmed the non-electrolytic structure of the NiII complex. Thermal decomposition of the NiII complex was shown to yield a metal oxide and OCH3 as residue. The octahedral geometry of the NiII complex was confirmed by microanalysis, mass spectroscopy, UV-Vis, magnetic susceptibility and FT-IR spectroscopy. The NiII complex was evaluated for its in vitro antioxidant activity by DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity and CUPRAC (cupric ion reduction capacity) in vitro bioanalytical methods. According to the CUPRAC method, the synthesized NiII complex was found to have potent antioxidant activity. In contrast to standard antioxidants, the NiII complex did not scavenge DPPH radical solution.