Available online at www.derpharmachemica.com Scholars Research Library Der Pharma Chemica, 2013, 5(4):120-125 (http://derpharmachemica.com/archive.html) ISSN 0975-413X CODEN (USA): PCHHAX 120 www.scholarsresearchlibrary.com Synthesis, spectral and antioxidant assay of Nickel (II) adducts with heterocyclic bases derived from 5-chloro-2-hydroxy acetophenone N(4) methyl thiosemicarbazone J. R. Gujarathi * , N. S. Pawar and R. S. Bendre a a School of Chemical Science, NMU, Jalgaon *Pratap College, Amalner (M.S.) _____________________________________________________________________________________________ ABSTRACT We have synthesized heterocyclic base adducts [pyridine (py), 2,2’-bipyridine (bipy), 1,10-phenanthroline (Phen), α/β-picoline] of Nickel (II) complexes by the reaction of Nickel (II) chloride with 5-chloro-2-hydroxy acetophenone N(4) methyl thiosemicarbazone in presence of heterocyclic base. Ligand was characterized by 13 C, 1 H NMR as well as IR, electronic spectra. The synthesized adducts were characterized by IR, ESI-MS, UV-visible, magnetic measurement, molar conductivity, TGA and DSC. The magnetic and spectroscopic data indicate a square planner geometry for the four coordinate and a distorted square pyramidal for five coordinate complexes. The Nickel (II) bipy and Nickel (II) β–pico adducts show higher antioxidant activity. Keywords: Thiosemicarbazone, Bioactive metal complexes and antioxidant activity. _____________________________________________________________________________________________ INTRODUCTION Thiosemicarbazones are the compounds used in the treatment of many diseases, for ex: cancer and its development is in progress [1-3]. Aromatic o-hydroxyaldehydes and ketones have biological properties. These thiosemicarbazones co-ordinate as the dianion to form mononuclear as well as binuclear complexes with the metal ion on deprotonation of the ring hydroxyl group and the loss of the N(2) hydrogen of the thiosemicarbazone moiety. In recent years, such thiosemicarbazones and their transition metal complexes have been studied due to their pharmacological interest [4,7]. The most promising areas in which thiosemicarbazone compounds are developed is their use against cancer. The presence of metal ion in thiosemicarbazone complexes increases the activity or contributes to migrate the side effects of the organic parent compounds [8]. The main known effects related to their anticancer activity are reactive oxygen species (ROS) production [9], topoisomerase II inhibition [10], mitochondria disruption [11] and amultidrug resistance protein (MDRI) inhibition [12,13] 3-aminopyridine-2-carboxaldehyde thiosemicarbazone has been developed as an anticancer drug and has in clinical phase II on several cancer types [14,15]. In recent years coordination complexes of transition metals have been the subject of detailed investigation [16-19]. Among these transition metals Ni (II) is recognized as an essential trace element for bacteria, plants, animals and humans. It has wide applications in industrial homogeneous catalysis [20, 59]. There can be many attractive structures and frameworks with many ligands [21-23]. Backbones with desirable structures and properties can be created by controlling coordination environment. The first crystal of Ni (II) complex with phen-dione as a ligand was reported [18]. Thiosemicarbazones exist in two tautomeric forms, thione and thiol. The thione functions as bidentate neutral ligand and the thiol can deprotonate and act as an anionic ligand [24]. As a part of studies on