Available online www.jocpr.com Journal of Chemical and Pharmaceutical Research, 2012, 4(3):1638-1643 Research Article ISSN : 0975-7384 CODEN(USA) : JCPRC5 1638 Transition metal complexes of 2-(substituted-1H-pyrazole-4-yl)-1H- benzo[d]imidazoles: Synthesis and characterization Minaxi Maru 1 and M. K. Shah* 2 1 Chemical Research Laboratory, Department of Chemistry, Saurashtra University, Rajkot, Gujarat, India 2 Department of Chemistry, Saurashtra University, Rajkot, Gujarat, India ______________________________________________________________________________ ABSTRACT Four novel monodentate 2-(3′-(4″-sub-aryl)-1′-phenyl-1H-pyrazole-4-yl)-1H-benzo[d]imidazole ligands (La-d) have been synthesized via the cyclocondensation of o-phenelyndiamine with 1,3-disubstituted pyrazole aldehydes by adding oxidizing agent ceria ammonium nitrate as catalyst in presence of hydrogen peroxide in alcoholic media. The non chelated Cu(II) and Ni(II) complexes of newly synthesized monodentate 2-substituted benzimidazole (La-d) ligands were prepared in 1:2-metal:ligand stoichiometry. The monodentate behavior of the ligand was confirmed on the basis of spectral studies. The Ni(II) complexes exhibits tetrahedral geometry where as Cu(II) complexes exhibits square planar geometry around the metal center. Key words: Monodentate 1H-benzimidazole, Non chelated Cu(II) and Ni(II) complexes, Pyrazole aldehydes. ______________________________________________________________________________ INTRODUCTION The coordination ability of a number of monodentate benzimidazole derivatives has been reported in past literature [1-6]. Numerous complexes involving d-block metals and imidazole derivatives are well known [7-13] and there is enormous interest in the transition metal complexes of imidazole and its derivatives as ligands [14-18]. Parasitic and antiviral activities of benzimidazoles and some substituted benzimidazole compounds have been widely investigated in medicinal fields. In medicine, drugs based on benzimidazoles and benzimidazole derivatives have been patented, due to their antiviral and antihelmintic activity [19]. In metallurgy, benzimidazole has been used as a corrosion inhibitor [20]. Benzimidazole as its 5,6-dimethyl derivative is present in vitamin, B 12 and related biomolecules. Coordination complexes of benzimidazole derivatives with transition metals have been used in attempts to prepare structural and spectroscopic models of the active sites of some metalloenzymes [21]. Reaction of the benzimidazole ligands with hydrated copper(II) and nickel(II) salts in ethyl alcohol led us to the formation of monodentate benzimidazole complexes M(La-d) 2 Cl 2 (Where, M = Cu(II) and Ni(II). The synthesized benzimidazole ligands (La-d) are an N- monodentate ligand that contains one donor group of relevance to the coordination of metal centers. In the present paper, we reported the synthesis and structural characterization of the dichloro-bis(La-d)metal(II) complexes.