Chemistry, Urease Inhibition, and Phytotoxic Studies of Binuclear Vanadium(IV) Complexes

Abstract

Vanadium plays an important role in biological systems and exhibits a variety of bioactivities. In an effort to uncover the chemistry and biochemistry of vanadium with nitrogen- and oxygen-containing ligands, we report herein the synthesis and spectroscopic characterization of vanadium(IV) complexes with hydrazide ligands. Substituents on these ligands exhibit systematic variations of electronic and steric factors. Elemental and spectral data indicate the presence of a dimeric unit with two vanadium(IV) ions coordinated with two hydrazide ligands along with two H(2)O molecules. The stability studies of these complexes over time in coordinating solvent, DMSO, indicates binding of the solvent molecules to give [V2O2L2(H2O)2(DMSO)2]2+ (L=hydrazide ligand) and then conversion of it to a monomeric intermediate species, [VOL(DMSO)3]1+. Hydrazide ligands are inactive against urease, whereas vanadium(IV) complexes of these ligands show significant inhibitory potential against this enzyme and are found to be non-competitive inhibitors. These complexes also show low phytotoxicity indicating their usefulness for soil ureases. Structure-activity relationship studies indicate that the steric and/or electronic effects that may change the geometry of the complexes play an important role in their inhibitory potential and phytotoxicity.

Synthesis, Spectroscopy, and Biological Properties of Vanadium(IV)–Hydrazide Complexes

“…The oxovanadium(IV) -ligand (1 : 1) complexes 1 -10 were synthesized by heating a mixture of the appropriate ligand and vanadyl sulfate in an equimolar ratio. The physical, analytical, and spectroscopic data of 1 -5 are collected in Table 1; those of 6 -10 have been reported previously [17] [18].…”

Enzyme inhibition, radical scavenging, and spectroscopic studies of vanadium(IV)–hydrazide complexes

“…Upon V(IV) complexation, the intense amide C=O band was shifted to a lower frequency, indicating coordination through the amide O-atom. All complexes exhibit strong V=O symmetric stretching absorptions around 981 ± 25 cm −1 , which are close to the V=O stretching frequency reported for other related oxovanadium(IV) complexes 31,[45][46][47][48] . These peaks are absent in parent ligands.…”

“…The product was dried in air. Physical and analytical data of oxovanadium complexes 1c-6c are given in Table 2, whereas those of 7c-11c are reported elsewhere 28,31 .…”

“…Hydrazide ligands were synthesized using a published procedure, and they exhibited similar structures to those reported elsewhere for other hydrazide ligands 28,31 . The spectral and analytical data of ligands 1-6 are given in Table 1, whereas those of 7-11 are reported elsewhere 28,31 .…”

Synthesis, crystal structures, and urease inhibition of an acetohydroxamate-coordinated oxovanadium(V) complex derived from N′-(3-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide

“…[11][12][13][14] It is notable that Ara and co-workers reported that some hydrazide ligands are inactive against urease, whereas their vanadium(IV) complexes show significant inhibitory potential against this enzyme and are found to be non-competitive inhibitors. 15 Aslam and co-workers reported that Schiff bases of hydrazone type also possess urease inhibitory activities. 16 Recently, our research group has reported some vanadium complexes with urease inhibitory activities.…”