A DETAILED SPECTROSCOPIC STUDY OF QUADRAVALENT OXOVANADIUM COMPLEXES OF AROYLHYDRAZINE

Vanadium is known to exhibit several bioactivities and shows its potential for its use as a pharmaceutical drug. Much of the research is underway in exploring bioactivities of vanadium complexes and understanding the mechanism of its biological properties. In an effort to uncover the chemistry and biochemistry of potential bioactive vanadium compounds, the synthesis and characterization of the oxovanadium(IV) complexes of aroylhydrazine ligands with systematic variation of electronic and steric factors is reported here. Enzyme inhibition studies with urease, phosphodiesterase and alpha-glucosidase along with leishmanicidal activity, immunomodulatory activity and radical scavenging properties of these complexes are determined to explore the structure function relationship.\ud \ud Twelve aroylhydrazine ligands with systematic variation of susbtitutents and their vanadium(IV) complexes are synthesized and characterized by using different spectroscopic techniques. Physical, magnetic and spectral data supports the presence of a dimeric structure in which each vanadium is coordinated with four coordinating atoms of two aroylhydrazine ligands and an oxygen atom of water molecule. IR spectra support the coordination of aroylhydrazine ligands through carbonyl oxygen and amine nitrogen. Vanadium-aroylhydrazine complexes exhibit the subnormal values of magnetic moments suggesting the dimeric nature of complexes. Similar values of magnetic moment, conductivity and spectral characteristics of different complexes may indicate existence of similar structure of the complexes.\ud \ud UV -vis spectra support the square pyramidal coordination of vanadium centers. The stability of different complexes in solution of coordinating solvent DMSO (dimethylsulpxide) is very different over time. These studies indicate binding of DMSO molecule at sixth position of both vanadium centers keeping the dimeric structure intact. Over time these species are converted to monomeric specie in which both solvent molecule and aroylhydrazine ligands are coordinated with the vanadium centre.\ud \ud Most of the ligands are inactive against urease, phosphodiesterases and alpha glucosidases, whereas, after coordination with vanadium they show very promising inhibitory potential against these enzymes. Al complexes exhibit non-competitive inhibition against all the enzymes. To understand the role of these complexes towards free radicals which play important role in several diseases including diabetes and its complications, we studied free radical scavenging properties of these complexes against DPPH and superoxide free radical. Leishmanicidal activity studies show varying degree of activities for aroylhydrazine and their vanadium(IV)-aroylhydrazine complexes. 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 enzyme inhibitory potential, radical scavenging activity and phytotoxicity.\ud \ud Oxovanadium(N) complexes of aroylhydrazine were screened for their immunomodulatory activity using normal and cancer cell lines. The cell lines used in these studies include normal fibroblast 3T3, beside the Prostate cancer (PC-3), cervical cancer Hela and C33A cell lines. Compounds found significantly active, but non-toxic in our systems could be used as immunosuppressive or anti-inflammatory agents. However, the exact mechanism and the nature of their immunomodulatory activity need to be further investigated