ASIAN JOURNAL OF CHEMISTRY ASIAN JOURNAL OF CHEMISTRY https://doi.org/10.14233/ajchem.2018.21068 INTRODUCTION Depending on tautomerism, hydrazones exhibits chela- ting behaviour. According to the number and type of the substituents in the hydrazone framework, the coordination mode gets influenced. The linkage of hydrazone to a metal ion depends on many factors which includes tautomerism, reaction conditions,stability of the complex formed, number and nature of the substituents on the hydrazone skeleton [1- 3]. Metal complexes containing acid hydrazones are found to serve as catalysts in several organic transformation reactions such as polymerization, epoxidation, reduction, oxidation, alkylation and condensation. Tahseen et al. [4] have found the catalytic abilities of oxovanadium complexes with hydrazones. They proposed that the complexes are very effective in the conversion of benzoin to benzil. One of the characteristic attribute of oxovanadium is the possibility to tune the electronic and steric properties of complexes. Hydrazones on coordi- nation to metal center through the iminol form facilitates the conjugation and enhances the nonlinearity [5,6]. Cariati et al. [7] and Naseema et al. [8] have studied the second order non- linear optical parameters of copper and palladium complexes of N-salicylidiene-N'-aroylhydrazines. They have proposed the third order non-linear optical properties of some hydrazones derived from p-tolyloxyacetohydrazide and have observed that the compounds exhibit optical limited behaviour. Paramagnetic Mononuclear Oxovanadium(IV) Complex as Oxidation Catalyst JYOTHY G. VIJAYAN Department of Chemistry, Christ University, Bengaluru-560 029, India Corresponding author: E-mail: jyothy.vijayan@res.christuniversity.in Received: 28 September 2017; Accepted: 31 January 2018; Published online: 29 March 2018; AJC-18822 2-Thiophenecarbanicotinic hydrazone is added with equimolar mixture of vanadyl acetyl acetonate in methanol to obtain oxovanadium(IV) complex of 2-thiophenecarbanicotinic hydrazone. Oxovanadium(IV) complex of 2-thiophenecarbanicotinic hydrazone is acted as an effective catalyst in the process. The catalytic reactions were carried under room temperature. The products generated were benzil and furil. The influence of solvent, oxidant and quantity of catalyst has been investigated. Oxovanadium(IV) complex of 2-thiophenecarba- nicotinic hydrazone proves significantly higher catalytic activity towards oxidation of secondary alcohols to ketones. The catalyst was proved to be very effective due to its recovery by simple filteration after completion of the reaction. It was reused several times which suggests that there is no change in the catalytic efficiency. Oxovanadium(IV) complex of 2-thiophenecarbanicotinic hydrazone did not show any leaching during the reaction, confirmed the heterogeneous nature. Keywords: Oxovanadium(IV) complex, 2-Thiophenecarbanicotinic hydrazone, Catalytic activity, Oxidation reactions. Asian Journal of Chemistry; Vol. 30, No. 5 (2018), 972-974 Oxovanadium complexes are found to be effective catalysts. As potential catalysts oxovanadium complexes can influence the yields of products and selectivity in many reactions [9,10]. Due to their catalytic efficiencies, oxovanadium complexes have been commonly utilized as precatalysts for epoxidation reactions. Vanadium catalyzed oxidation reactions has attracted several chemists because of the selectivity, reactivity and stereo- selectivity [11]. The catalyst showed high stability, reactivity, and efficiency under various reaction conditions and solvents. The catalysts can be recycled and reused without showing much metal leaching. EXPERIMENTAL 2-Thiophene carboxaldehyde, nicotinic hydrazide, benzil, furil, methanol, glacial acetic acid, vanadyl acetylacetonate and acetone were procured from Sigma Aldrich and used without further purification. 1 H NMR spectra were recorded on Bruker AMX 400 FT-NMR spectrometer with DMSO-d 6 as solvent and TMS as internal standard. Preparation of heterogeneous catalyst 2-thiophene- carbanicotinic hydrazonato oxovanadium(IV): To a solution of 2-thiophenecarbanicotinic hydrazone (0.23 g, 1 mmol) in methanol (20 mL), vanadyl acetylacetonate (0.27 g, 1 mmol) dissolved in methanol (20 mL) was added. The reaction mixture was stirred at room temperature with a magnetic stirrer