Synthesis, characterization, semi-empirical study and alkaline phosphatase activity of vanadyl(IV) complexes with N/O- and O-donor ligands Khurram Shahzad Munawar 1 , Saqib Ali* 1 , Allah Nawaz Khan 2 , Saira Shahzadi 3 , Saroj K.Sharma 4 , Kushal Qanungo 4 1 Department of Chemistry, Quaid-i-Azam University, Islamabad - 45320, (PAKISTAN) 2 Department of Biochemistry, Capital Hospital, CDA, Islamabad, (PAKISTAN) 3 Department of Chemistry, GC University, Faisalabad, (PAKISTAN) 4 Deptartment of App. Sci. and Hum., Faculty of Engg. and Tech., Mody Institute of Technology and Science (Deemed University), Lakshmangargh - 332 311, Dist Sikar, Raj., (INDIA) E-mail: drsa54@yahoo.com; sairashahzadi@hotmail.com Received: 6 th March, 2012 ; Accepted: 6 th April, 2012 Full Paper KEYWORDS Vanadyl(IV) complexes; Spectroscopy; Conductance; Semi-empirical study; Alkaline phosphatase activity. ABSTRACT Various N/O- and O-donor ligands and their vanadyl(IV) complexes have been synthesized and characterized by different techniques such as FTIR, elemental analysis, thermogravimetery and conductometry. The IR data shows the bidentate nature of the ligands and reveals hexa-coordinated geometry in the solid state which is also confirmed by semi-empirical study. Conductance measurements reveal the non-electrolytic nature of the com- plexes. These complexes have been checked for their alkaline phosphatase activity in the presence and absence of inhibitor which shows that by the addition of inhibitor the activity of enzyme decreases and at higher concen- tration it is completely inhibited.  2012 Trade Science Inc. - INDIA INTRODUCTION Vanadium compounds show interesting biochemi- cal and pharmacological properties [1] . Intensive studies carried out over the last two decades [2] showed that vanadium is one of the most important supplements for oral diabetes therapy [3] . Inorganic vanadium salts are poorly absorbed from the digestive system, thus high oral doses are required. Therefore, various vanadium ionsorganic ligand complexes were tested in order to obtain more potent medicines than inorganic vanadium salts [4] . Enzymes containing vanadium as an essential element were isolated in the 1980 s. These enzymes are able to exercise the activities of nitrogenase and bromoperoxydase 1 . Presently, numerous papers deal with the vanadium biochemistry [1,5] . Several vanadium compounds have recently been investigated in animal model systems as treatment for diabetes [6,7] and studies in clinical trials in human beings with organic transition metal complex have been developed [8] . Tetradentate schiff base complexes of oxovanadium(IV), VO 2+ , have been the subjects of various studies [9-15] . The use of chiral oxovanadium(IV) complexes in the preparation of chiral sulfoxide for the pharmaceutical industry has been widely studied [9,10] . Other area of great interest is the role of the vanadium species in oxygen atom or electron transfer reactions [5] . Vanadium(IV) complexes with Schiff bases encap- ICAIJ, 7(2), 2012 [82-93] An Indian Journal Trade Science Inc. Volume 7 Issue 2 Inorganic CHEMISTRY ISSN : 0974 - 746X