Synthesis, ab initio calculations, thermal, thermodynamic and antioxidant properties of some oxovanadium(IV) complexes containing N2O2 set of donor atoms

The formation constants of some oxovanadium(IV) binary complexes containing Schiff bases resulting from condensation of salicylaldehyde with aniline and with its derivatives were determined spectophotometrically. The synthesized compounds were characterized by analytical and different physico-chemical techniques like ¹H NMR, IR, elemental analysis, mass and UV-Vis spectral studies. The IR spectra affirm that coordination takes place through azomethine nitrogen and phenolate oxygen. Three of the VO(IV) Schiff base complexes i.e. bis(salicylideneaniline)oxovanadium(IV), VO(L¹)₂], bis(salicylidene-4-methoxyaniline) oxovanadium (IV), VO(L²)₂] and bis(salicylidene-4-cyanoaniline)oxovanadium(IV), VO(L¹⁰)₂], were studied by thermogravimetry in order to evaluate their thermal stability and thermal decomposition pathways. The number of steps and, in particular, the starting temperature of decomposition of these complexes depends on the equatorial ligand. The complexes screened for antioxidant activity and the ab initio calculations were carried out to determine the structural and the geometrical properties of a typical vanadyl salicylideneaniline complex, VO(L¹)₂].