www.jocpr.com Available online Journal of Chemical and Pharmaceutical Research, 2013, 5(10):206-217 Research Article ISSN : 0975-7384 CODEN(USA) : JCPRC5 206 Synthesis, characterization and biological activity of salen-mixed ligand complexes with nickel(II), copper(II) and cobalt(III) Akmal S. Gaballa Faculty of Specific Education, Zagazig University, Zagazig, Egypt _____________________________________________________________________________________________ ABSTRACT The mixed Schiff base ligand, N,N′-o-phenylenebis(salicylideneimine) (H 2 salen) with the ligands 4- aminoantipyrine (AAP) or ammonium pyrrolidinedithiocarbamate (APDC) were reacted with Ni(II), Cu(II) and Co(II) acetates. Four new different complexes were prepared and formulated as [Ni 2 (salen)(CH 3 CO 2 ) 2 (AAP) 2 ] (1), [Ni 2 (salen)(CH 3 CO 2 ) 2 (PDCH) 2 ]·2H 2 O (2), [Cu 2 (salen)(CH 3 CO 2 ) 2 ]·2H 2 O (3) and [Co(salen)(CH 3 CO 2 )]·(H 2 O) (4). The H 2 salen ligand and its complexes were characterized by IR, UV-visible, TG, elemental analyses, and molar conductivities. The complexes were proposed to be distorted octahedral geometry with Ni(II) and Co(III) and distorted square planar geometry with Cu(II). Antibacterial activity of the complexes was tested against selected bacteria by agar well diffusion method. Keywords: Schiff base-mixed ligands; M(II/III) complexes; Spectroscopic, Thermal analysis; Antimicrobial activity. _____________________________________________________________________________________________ INTRODUCTION Interaction of Schiff base compounds with metal ions and their metal complexes have been extensively investigated due to their wide range of applications in medicine and engineering [1-8]. In recent years, there has been a considerable interest in the chemistry of antipyrine and its derivatives such as 4-aminoantipyrine (AAP, Fig. 1) or their metal complexes. These compounds are reported to exhibit a wide range of applications in various fields like biological properties as antifungal, antibacterial, analgesic, sedative, antipyretic, anti-inflammatory agents, analytical and therapeutical [9-18]. Pyrrolidinedithiocarbamates (PDC) which represent a class of antioxidants mediate a wide variety of effects in biological systems [19]. It is a multipotent synthetic compound well known for its metal chelation property [20]. Also, ammonium pyrrolidinedithiocarbamate (APDC, Fig.1) has been used recently in various preconcentration and separation techniques [21-25]. APDC is most widely used to determine the metal ions that form slightly soluble complexes in an aqueous solution [26]. The most motivating features of these ligands are the possibility of using them to synthesize complexes with different modes of bonding and their interesting biological activity. In recent years, there has been considerable interest in the complexes formed by H 2 salen (Fig. 1), AAP, APDC and acetate ligands as they are common components of some biologically important molecules. As a part of our continued research work on synthesis, characterization and biological activity, the present paper describes the synthesis and characterization of new Ni(II), Cu(II) and Co(III) complexes with H 2 salen mixed ligands. Thermal analysis is also helpful to study the chemical structure and thermal parameters of the complexes [27-29]. The study of the structural behavior of the complexes derived from the reaction of the metal ions, Ni(II), Cu(II) and Co(II) and with mixed H 2 salen donor ligands is a matter of significant importance for the investigation of the geometries of the formed complexes during decomposition processes. The prepared metal complexes were screened for their in vitro antimicrobial activities