Synthesis and characterization of mononuclear oxovanadium(IV) complexes and their enzyme inhibition studies with a carbohydrate metabolic enzyme, phosphodiesterase I

The increasing interest in vanadium coordination chemistry is based on its well-established chemical and biological functions. A β-diketonato complex of oxovanadium(IV) is known to be having numerous catalytic applications and also exhibits promising insulin mimetic properties. In continuation of our structure activity relationship studies of metal complexes, we report herein the synthesis and characterization of the vanadium complexes of β-diketonato ligand system with systematic variations of electronic and steric factors. Two complexes, VO(tmh)2 (tmh = 2,2,6,6-tetramethyl-3,5-heptanedione), and VO(hd)2 (hd = 3,5-heptanedione) were synthesized and characterized by using different spectroscopic techniques. Elemental and mass spectral analysis supports the presence of two β-diketonato ligands per VO2+ unit. UV-Vis spectra in different solvents indicate coordination of coordinating solvent molecules at sixth position resulting in red shift of the band I transition. NMR and IR spectra reveal binding of coordinating solvent molecule at vacant sixth position trans to oxo group without releasing β-diketonato ligands. Enzyme inhibition studies of these and other related oxovanadium(IV) complexes with β-diketonato ligand system are conducted with snake venom phosphodiesterase I (SVPDE). All of these complexes showed significant inhibitory potential and were found to be non-competitive inhibitors against this enzyme.