title: 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.
authors.affiliation: Department of Chemistry, University of Karachi, Karachi-75270, Pakistan.
authors.forename: Rifat
authors.initials: R
authors.lastname: Ara
authors.forename: Uzma
authors.initials: U
authors.lastname: Ashiq
authors.forename: Mohammad
authors.initials: M
authors.lastname: Mahroof-Tahir
authors.forename: Zahida Tasneem
authors.initials: ZT
authors.lastname: Maqsood
authors.forename: Khalid Mohammed
authors.initials: KM
authors.lastname: Khan
authors.forename: Muhammad Arif
authors.initials: MA
authors.lastname: Lodhi
authors.forename: Muhammad Iqbal
authors.initials: MI
authors.lastname: Choudhary
mesh_terms: D004791:Enzyme Inhibitors / Q000494:pharmacology*; D010944:Plants / Q000187:drug effects*; D014510:Urease / Q000037:antagonists & inhibitors*; D017968:Vanadium Compounds / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D017968:Vanadium Compounds; D014510:Urease