Hindawi Publishing Corporation Journal of Chemistry Volume 2013, Article ID 947325, 5 pages http://dx.doi.org/10.1155/2013/947325 Research Article Synthesis of Oxovanadium(IV) Complexes with Tetraaza Coordinating Ligands Sanjay Singh, 1 Hardeo S. Yadav, 2 Ashok Kumar Yadava, 2 and Devendra Pratap Rao 3 1 Department of Chemistry, MGPG College, Gorakhpur 273001, India 2 Department of Chemistry, North Eastern Regional Institute of Science and Technology (NERIST), Arunachal Pradesh, Nirjuli 791109, India 3 Department of Chemistry, D.A-V. (P.G.) College, Kanpur 208001, India Correspondence should be addressed to Devendra Pratap Rao; devendraprataprao@yahoo.com Received 18 June 2012; Accepted 28 August 2012 Academic Editor: Alexander Kornienko Copyright © 2013 Sanjay Singh et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Oxovanadium(IV) complexes of the type [VO(mac)]SO 4 (where mac = tetraaza macrocyclic ligands derived by condensation of thenil with 1,4-diaminobenzene or 3,4-diaminopyridine and their reaction with -diketones) have been prepared using vanadyl ion as kinetic template. e prepared macrocyclic complexes were characterized by elemental analyses, molar conductance, magnetic moments, and infrared, electronic, and electron spin resonance data. �rom the spectroscopic studies, �ve-coordinate s�uare- pyramidal geometry for the VO 2+ complexes have been proposed wherein derived ligands act as tetradentate chelating agents. 1. Introduction e chemistry of vanadium has generated great interest since the discovery of vanadium in organisms such as certain ascidians and Amanita mushrooms and being a constituent of the cofactors in vanadate-dependent haloperoxidases and vanadium nitrogenase [1–3]. e literature contains sev- eral reports about oxovanadium(IV) complexes which show modulating activities of various enzymes [4, 5]. Vanadium compounds with vanadyl ion having oxidation state +4 and +5 exist in the environment and in biological systems. ese complexes also have biological activities such as antibacterial, antifungal, antiviral, and anticancer drugs [6–8]. enil is a versatile chelating agent having two reactive carbonyl groups capable of undergoing Schiff-base condensation with a variety of di- and polyamines. e use of metals as templates in such reaction has led to the synthesis of metal complexes of macrocyclic ligands [9]. us, thenil has played an important role in the development of macrocyclic complexes. Such complexes show unusual structure and stability and are known to have relevance to biological system. is provides an opportunity to design and study the model biological systems to understand the chemical changes taking place in such cases [10]. However, in most cases, the template effect of metal ions of the �rst transition series has been studied and the chemistry of metal complexes with macrocyclic ligands of oxovanadium(IV) incorporating four nitrogen donor atoms has received less attention[11, 12]. With this aspect, some oxovanadium(IV) complexes with new denticity ligands derived from condensation of thenil with 1,4-diaminobenzene or 3,4-diaminopyridine, capable of undergoing cyclization with -diketones via the metal template effect, have been prepared and characterized, and their tentative structures are ascertained in this communica- tion. 2. Experimental 2.1. Chemicals and Materials. All the chemicals and the solvents used were of the reagent grade. Oxovanadium(IV) sulfate was procured from Aldrich Chemical Co. e - diketones, namely, acetylacetone, benzoylacetone, thenoyl- tri�uoroacetone and dibenzoylmethane, were SRL products and the diamines used were reagent-grade products. enil used was an Aldrich product.