Synthesis, Characterization, Thermal and Catalytic Studies of Oxovanadium(IV) Complexes with Tetradentate ONNO Donor Ligands

Oxovanadium(IV) complexes of N2O2 type Schiff bases derived by the condensation of 5-chloro-2-hydroxyacetopheneone or 5-chloro-2-hydroxy-3-nitroacetophenone with trans-1,2-diaminocyclohexane have been synthesized and characterized by elemental analysis, IR and electronic spectra, magnetic moments, ESR, XRD and thermal analysis. The thermal behaviour of the complexes has been assessed using TG-DTG analysis and both the complexes exhibit loss of crystal water in first step whereas ligand segments in the subsequent steps. The various kinetic and thermodynamic parameters such as Ea, Delta H, Delta S, Delta G have been calculated from the TG data. The complexes act as oxidation catalysts for the oxidation of styrene in presence of hydrogen peroxide. The solid state electrical conductivity of complexes show their semiconducting behavior. The geometry around oxovanadium(IV) in both complexes is square pyramidal. The IR spectra suggest bi-negative tetradentate nature of the ligands with ONNO donor sequence sites of the azomethine nitrogen and phenolic oxygen. The crystal system, lattice parameters and unit cell volume of both the complexes have been determined by XRD and belongs to monoclinic crystallized system.