DFT study of new biologically important oxidovanadium (IV) complexes of nitro-substituted benzohydroxamate ligands

The new oxidovanadium (IV) complexes of composition [VO(HL1,2)(2)] (I and II) (where HL1 = 3-NO2C6H4 CONHO] and HL2 = 3,5-(NO2)(2)C6H3 CONHO-); [VO(3-NO(2)BzH)(2)] (I), [VO(3,5-(NO2)(2)BzH)(2)] (II) have been synthesized by the reactions of VOSO4.5H(2)O with biologically important potassium salts of two nitro-substituted benzohydroxamate ligands (KHL (1; 2)) and thoroughly characterized by various spectral techniques. The gas phase optimized geometry computed by DFT/SIESTA code using standard conjugate-gradient (CG) technique has depicted distorted square-pyramidal geometry for complexes substantiated by index/angular structural parameter (tau), the mathematical assignment demonstrating plausible geometry and extent of distortion. The molecular properties viz. ionization potential (IP), electron affinity (EA), chemical potential (mu), hardness (eta), softness (S), electronegativity (chi) and electrophilicity index (omega) have been calculated from the energies of frontier molecular orbitals (HOMO-LUMO energy values) to have an insight into energy distortion and energetic behaviour. The chemical bonding and molecular orbital contributions have been computed from the density of states (DOS), partial density of states (PDOS) and overall population density of states (OPDOS)/COOP (Crystal orbital overlap population) methods. The vanadium (3d) and O, O (2p) orbitals of carbonyl and hydroxamic oxygen atoms have been found to involve significant bonding interactions substantiated by computed charge energy differences in complexes.