Synthesis, structural studies and antioxidant activities of M(II) complexes with NOS donor schiff base ligand

Schiff base ligand, (E)-methyl 6-acetamido-2-(5-bromo-2-hydroxybenzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate, was successfully prepared with condensation reaction. The newly obtained Schiff base used to synthesize five new complex,[FeLCl(H2O)(2)]center dot 1.5H(2)O, [CoLCl(H2O)(2)]center dot 2H(2)O, [NiLCl(H2O)(2)]center dot H2O, [RuLCl(p-cymene)]center dot 3.5H(2)O and [PdLCl center dot H2O]center dot 3H(2)O. From the magnetic and spectral data, the geometric structures of these complexes were found to be square planar and octahedral. The characterizations of ligand and complexes were done by FT-IR, UV-Vis, H-1 and C-13-NMR, microanalyses, magnetic susceptibility, mass spectra and thermogravimetry analysis (TGA) and further were screened for antioxidant activities. Antioxidant properties of synthesized compounds were examined using different methods including total antioxidant activity, FRAP (ferric reducing antioxidant power), CUPRAC (cupric reducing antioxidant capacity) and DPPH (2,2-diphenyl-1-picrylhydrazyl). The Ru(II), Pd(II), Fe(II) and Co(II) metal complexes generally exhibited good antioxidant properties.