Synthesis, structural characterization, thermal and electrochemical studies of Mn(II), Co(II), Ni(II) and Cu(II) complexes containing thiazolylazo ligands

Some thiazolylazo derivatives and their metal complexes of the type [M(L)(H2O)Cl]; M = Mn(II), Co(II), Ni(II), Cu(II) and L = 6-(2′-thiazolylazo)-2-mercapto-quinazolin-4-one (HL1), 6-(4′-phenyl-2′-thiazolylazo)-2-mercapto-quinazolin-4-one (HL2), 6-(2′-thiazolylazo)-2-mercapto-3-(m-tolyl)-quinazolin-4-one (HL3) and 6-(4′-phenyl-2′-thiazolylazo)-2-mercapto-3-(m-tolyl)-quinazolin-4-one (HL4) have been prepared. All the complexes were characterized on the basis of elemental analysis, molar conductance, magnetic moment, IR, UV-vis, ESR, TG-DTA and powder X-ray diffraction studies. IR spectra of these complexes reveal that the complex formation occurred through thiazole nitrogen, azo nitrogen, imino nitrogen and sulfur atom of the ligands. On the basis of electronic spectral data and magnetic susceptibility measurement octahedral geometry has been proposed for the Mn(II), Co(II) and Ni(II) complexes and distorted octahedral geometry for the Cu(II) complexes. Electrochemical behavior of Ni(II) complexes exhibit quasireversible oxidation corresponding to Ni(III)/Ni(II) couple along with ligand reduction. X-ray diffraction study is used to elucidate the crystal structure of the complexes.