New transition metal(ii) mixed-ligand complexes of phenylbutanedione and dithiocarbamate: synthesis, characterization, thermal and antioxidant studies

Abstract

Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) mixed ligand complexes of 1-phenyl-1,3-butanedione and N,N'-dimethyldithiocarbamate have been synthesized. The complexes were characterized by elemental and percentage metal analyses; magnetic moments, solubility and molar conductance measurements; and spectrophotometrically, by infrared, electronic, ESI mass, 1H and 13C-NMR spectra studies. The percentage metal, CHNS, magnetic moments, molar conductance, electronic, and IR data are corroborative of a non-electrolyte, mononuclear octahedral geometry for Fe(II), Co(II), Ni(II) and Cu(II) complexes and four-coordinate tetrahedral geometry for Mn(II) and Zn(II) complexes. The coordinations to the metal ions were found to be through the S2O2 chromophores, with the exception of Fe(II) complex, which was via the O4 chromophores of bis(1-phenyl-1,3-butanedione) ligand. The thermogravimetric analyses carried out revealed that the complexes are all thermally degradable and support the proposed formulae and, as well the ESI mass data. The antioxidant studies show that the Cu(II) and Co(II) complexes had higher percentage scavenging inhibition of 81.2 % and 71.9 % respectively, compared to the positive standard, ascorbic acid with inhibitory activity of 56.2 %.