Synthesis, spectroscopy, and biological properties of vanadium(IV)-hydrazide complexes.

The synthesis, spectroscopic, enzyme-inhibition, and free-radical-scavenging properties of a series of vanadium(IV) complexes, compounds 1-10, were investigated. These complexes exhibit a dimeric structure with hydrazide ligands coordinated in a bidentate fashion. All complexes are stable in the solid state, but exhibit varying degrees of stability in solution. In coordinating solvent such as DMSO, stepwise binding of two solvent molecules at the 6th positions trans to the V double bond O bond of the dimeric unit is observed. The dimeric compounds are converted to monomeric species in which both solvent molecules and the hydrazide ligands are coordinated to the V(IV) center. The free hydrazide ligands 11-20 were inactive against alpha-glucosidase, but the V(IV) complexes showed varying degrees of inhibition, depending on the type of ligand. The DPPH-radical-scavenging activities of 1-20 were determined, which indicated that steric and/or electronic effects responsible for changes in geometry play important roles in terms of antioxidant potential.