Electrochemistry, Thermalanalysis, and Theoretical Study of Vanadyl Schiff Base Complexes

The VO(IV) complexes of tridentate ONO Schiff base ligands derived from 2- aminobenzoicacid and salicylaldehyde derivatives were synthesized and characterized by IR, UV–Vis and elemental analysis. Electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good linear correlation was observed between the oxidation potentials and the electron-withdrawing character of the substituents on the Schiff bases, showed the following trend: MeO < H < Br < NO2. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the synthesized complexes were carried out in the range of 20–700 °C. All of the complexes decomposed in three steps. The thermal decomposition pathways were closely related to the nature of the Schiff base ligands and preceded via first-order kinetics. The structures of compounds were determined by ab initio calculations. The optimized molecular geometry was calculated at the B3LYP/6-31G(d) level. The results suggested that, in the complexes, V(IV) ion was in square-pyramid or TBP (trigonal bipyramidal) NO4 coordination geometry. Also the bond lengths and angles were studied and compared.