DOI:10.7598/cst2016.1234 Chemical Science Transactions ISSN:2278-3458 2016, 5(3), 587-594 Synthesis, Characterization and Antimicrobial Screening of Metal Complexes of Mannich Bases Derived from Benzimidazole A. ABDUL JAMEEL 1 , M. SYED ALI PADUSHA 1 , K. SULTHAN SYED IBRAHIM 2* and S. SAJENA 1 1 Department of Chemistry, Jamal Mohamed College, Tiruchirappalli-620020, Tamilnadu, India 2 Department of Chemistry, Dr. Zakir Husain College, Ilayangudi - 630702, Tamilnadu, India kssichem@gmail.com Received 5 March 2016 / Accepted 19 March 2016 Abstract: Co(II), Ni(II), Cu(II) and Zn(II) complexes of 2-((1H-benzo[d]imidazol-1-yl)(phenyl) methyl)hydrazinecarboxamide (BIBS) and 2-((1H-benzo[d]imidazol-1-yl)(phenyl) methyl) hydrazine- carbothioamide (BIBTS) were synthesized and characterized by elemental analysis, IR, 1 H NMR, 13 C NMR, mass, electronic spectra, magnetic moment, molar conductance and EPR studies. The complexes were found to have general formulae [M(BIBS) 2 Cl 2 ] and [M(BIBTS) 2 Cl 2 ] [M = Co(II), Ni(II), Cu(II) and Zn(II)]. The IR results demonstrate that co-ordination sites are the azomethine nitrogen and carbonyl oxygen atom of the ligand BIBS, carbonyl sulphur of the ligand BIBTS. The geometry of the complexes is confirmed by measuring number of bands, their energy positions and intensity by electronic and magnetic moment measurement values. The in vitro biological screening effects of the synthesized compounds were tested against various microbial species and the results show that the metal complexes are more biologically active than the free ligand. Keywords: Mannich base, Metal complexes of benzimidazole, O, N and O, S donor, Antimicrobial activity Introduction Mannich reaction withstands a large diversity of functional groups and hence it has been witnessing a continuous growth in the field of organic chemistry. The surge of literature on Mannich reaction provides an outstanding evidence for the diversity and applications of the reaction 1 . Mannich bases are physiologically reactive because of the basic function rendering the molecule soluble in aqueous solvent when it is transformed into ammonium salt 2 . Benzimidazole and its derivatives have different activities as they can act as bacteriostats or bactericides, fungicides, anticarcinogens, etc 3-6 . The biological activity and pharmacological properties of the benzimidazole derivatives, have led us to investigate the coordination behavior of benzimidazole derivatives towards transition metal ions. However, bis(benzimidazole) ligands, which represent a class of aromatic N-donor organic linkers, RESEARCH ARTICLE