New Insights into the Chemistry of Oxovanadium(IV) Complexes with N4 Coordinating Ligands

The syntheses of new oxovanadium(IV) complexes having general formula [VO(mac)]SO4 have been carried out by using in situ method of preparation where vanadyl ion acts as kinetic template for the ligands derived by condensation of 2,2′-pyridil with 1,2-diaminopropane and 1,3-diaminopropane. The complexes were characterized by elemental analyses, molar conductance, magnetic moments, and spectral (infrared, electronic, and electron spin resonance) data. All the oxovanadium(IV) complexes are five coordinate wherein derived ligands act as tetradentate chelating agents. 1. Introduction Vanadium is widely distributed in the biosphere and its essential role has been recognized in both plants and animals. The oxovanadium(IV) cation has been found to inhibit the plasma membrane ATPase of Neurospora crassa and Saccharomyces cerevisiae, the proton translocating ATPase of Mycobacterium phlei and Ca++-ATPase of red cell membranes [1–3]. It has been observed that the free vanadyl ion is oxidized to vanadate within a few minutes in aqueous solution exposed to air at neutral pH [4–6]. However, the tetravalent state appears to be stable when complexed with intracellular proteins or smaller molecules. Thus the complex formation of the oxovanadium(IV) cation with tetraaza ligands appears to be interesting, particularly in order to explore the biochemical importance of the oxovanadium(IV) cation in vitro at neutral pH [7–9].The coordination chemistry of vanadium has great interest since the discovery of vanadium in organisms such as certain ascidians and Amanita mushrooms and as a constituent of the cofactors in vanadate-dependent haloperoxidases and vanadium nitrogenases [10, 11]. Since then, extensive studies have been carried out to explore vanadium chemistry, including the synthesis of novel complexes and their antidiabetic activities both in vitro and in vivo [12–14]. Many clinical trials of vanadium compounds have also been reported [15–17], in which vanadium salts such as VOSO4 and NaVO3 were administered to diabetic patients. With this view, the oxovanadium(IV) complexes of ligands derived from condensation of 2,2′-pyridil with diamines, namely, 1,2-diaminopropane and 1,3-diaminopropane are synthesized. These complexes are characterized by elemental analyses, molar conductance, magnetic susceptibility, and spectral data. The tentative structures of these oxovanadium(IV) complexes are also ascertained on the basis of above characterization. 2. Experimental 2.1. Materials Oxovanadium(IV) sulfate was procured from Aldrich. The diamines used were reagent grade products.