Oxidovanadium(IV) complexes involving dehydroacetic acid and β-diketones of bioinorganic and medicinal relevance: Their synthesis, characterization, thermal behavior and DFT aspects

Six new mixed-ligand complexes of oxidovanadium(IV) of the general composition [Vo(dha)(L)(H2O)], where dhaH = dehydroacetic acid, LH = beta-diketones, viz., acetoacetanilide (aaaH), o-acetoacetotoluidide (o-aatdH), o-acetoacetanisidide (o-aansH), acetylacetone (acacH), methyl acetoacetate (matacH) or ethyl acetoacetate (eacacH) have been synthesized by the reaction of VOSO4 center dot 5H(2)O and the ligands given above in aqueous-ethanol medium. The resulting complexes have been characterized on the basis of elemental analyses, vanadium determination, molar conductance and magnetic measurements, mass spectrometry, thermogravimetric analysis, infrared and electron spin resonance spectral studies. The thermal decomposition processes of two representative complexes are discussed and the order of reaction (n) and the activation energy (E-a) for the particular decomposition steps have been calculated from thermogravimetric (TG) curve. Geometry optimizations were performed with the Gaussian 09 software package by using density functional theory (DFT) methods with Becke-3-Lee-Yang-Parr (B3LYP) hybrid exchangecorrelation functional and the standard LANL2 MB basis set for dhaH and its complex [VO(dha)(acac) (H2O)]. Molecular surface electrostatic potentials (MSEP), vibrational frequency calculations, bond lengths, bond angles, dihedral angles, natural population analysis and calculations of molecular energies, HOMO and LUMO were made. No imaginary frequency was found in the optimized model compounds and hence ensures that the molecule is in the lowest point of the potential energy surface, that is, a energy minimum. Finally calculated results were applied to simulated Infrared spectra of the title compound which show good agreement with observed spectra. Based on experimental and theoretical data, suitable trans-octahedral structures have been proposed for these complexes. (C) 2014 Elsevier B.V. All rights reserved.