Ligand role on insulin-mimetic properties of vanadium complexes. Structural and biological studies

The syntheses of 16 vanadium(IV and V) complexes with ONO tridentate Schiff base ligands are described. The vanadium(IV) compounds were synthesized with 1,10-phenantroline as a co-ligand. In the case of five complexes of vanadium(V), the solvent molecule in form of ethanol or ethoxy ligand fill the coordination sphere of V(V) to six. In the crystal structure of selected complexes the mixture of isomers in 1:1 ratio in the unit cell is observed as the ligand is not symmetrical and forms both 5- and 6-membered rings in complex. All complexes were characterized also by elemental analysis, IR and UV-Vis spectroscopy, magnetic and cyclic voltammetry measurements. The stability of the complexes in DMSO-H2O mixture was performed at pH = 7.0 and 2.0. The relationship between phosphatase inhibition and cytotoxicity of the compounds and the key role of organic ligands in enhancing biological activity of vanadium complexes was also discussed.