N2O2-complexes of oxovanadium(IV) with 2,2 '-dihydroxybenzophenone thiosemicarbazones: Synthesis, EPR and electrochemical studies

Abstract

The S-alkyl thiosemicarbazone derivatives of 2,2'-dihydroxybenzophenone thiosemicarbazones (alkyl: methyl, propyl and allyl) and their oxovanadium(IV) chelates were synthesized. The solid complexes in the general formula [VO(L)] were characterized by elemental analysis, magnetic measurements, IR, UV-Vis and EPR spectroscopy. The X-band EPR signals recorded from powder forms and also in solution. All samples have a single asymmetric line shape and theoretical fit studies proved the presence of axial symmetry around the paramagnetic vanadium ions. A computer simulation of the EPR spectrum of each sample has been carried out to derive the related EPR parameters. The electrochemical behaviors of the complexes examined by cyclic voltammetry (CV) are found similar. They give a metal-based one-electron quasi-reversible redox couple near 500 mV corresponding to V-IV/O-V process and a cathodic peak near -800 mV irreversible reduction of (VO)-O-IV to (VO)-O-III which are consistent with hydrodynamic voltammograms. The additional peaks in the CVs growing with the scan rate can be attributed to consecutive one-electron reduction of ligand. (C) 2013 Elsevier Ltd. All rights reserved.