Spectroscopic and theoretical study of 1,2,4-triazole-3-one based salicylaldimine complexes and evaluation of superoxide-scavenging properties

Five mononuclear metal complexes of Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized with a triazole-based Schiff base ligand, 4-{[(1E)-(2-hydroxyphenyl)methylene]amino}-5-(2-thienyl-methyl)-2,4-dihydro-3H-1,2,4-triazol-3-one. The structure of the compounds have been proposed by elemental analyses, spectroscopic data i.e. IR, 1H and 13C NMR, UV–vis, electrospray ionisation mass spectra, molar conductivities and magnetic susceptibility measurements. The molecular structure and vibrational frequencies of the compounds in the ground state has been calculated by density functional using Becke’s three-parameter hybrid method with the Lee, Yang and Parr correlation functional methods with the Standard B3LYP/6-31G*(d,p) basis set. The computational frequencies are in good agreement with the experimental results. The superoxide dismutase (SOD) mimetic activity of the complexes have been investigated by utilizing xanthine–xanthine oxidase assay. The results indicate that the Co(II) complex is the most potent SOD mimetic of all synthesized complexes.