Synthesis, Structural, and Insulin-Enhancing Studies of Oxovanadium(IV) Complexes

Oxovanadium(IV) complexes with Schiff bases derived from substituted salicylaldehyde and diamine have been prepared and characterized. H-1 NMR and IR spectral data revealed that the symmetrical Schiff base was isolated, and elemental analysis confirmed the purity of all the compounds as formulated. The room-temperature magnetic moments of 1.6-1.8 Bohr magneton for the complexes confirmed that the complexes are V-IV complexes, with d(1) configuration. Cyclic voltammetry revealed only one quasi-reversible wave for each complex and they all showed redox couples with peak-to-peak separation values (Delta E-p) ranging from 76 to 84 mV, indicating a single-step one-electron transfer process. An oral administration of these complexes supplied at a dose of 0.2 mmol kg(-1) to streptozotocin-induced diabetic rats elicited a progressive reduction in plasma glucose over 6-h periods. Two of the complexes produced significant and consistent reduction in fasting blood glucose levels over a 6-h monitoring period.