Available on line www.jocpr.com Journal of Chemical and Pharmaceutical Research __________________________________________________ ISSN No: 0975-7384 CODEN(USA): JCPRC5 J. Chem. Pharm. Res., 2011, 3(3):196-204 196 Synthesis, characterisation and biological activities of Mn(II), Co(II) and Ni(II) complexes of hexamethylenetetramine M.O. Agwara 1* , M.D. Yufanyi 2 , J.N. Foba-Tendo 2 , M.A. Atamba 1 and Derek Tantoh Ndinteh 3 1 Coordination Chemistry Laboratory, Department of Inorganic Chemistry, Faculty of Science, University of Yaoundé I, P.O. Box 812 Yaoundé, Cameroon 2 Department of Chemistry, Faculty of Science, University of Buea, P.O. Box 63 Buea, Cameroon 3 Department of Chemical Technology, University of Johannesburg, P.O. Box 17011, Doorfontein, South Africa ______________________________________________________________________________ ABSTRACT Mn(II), Co(II) and Ni(II) complexes of hexamethylenetetramine (HMTA) have been synthesized in water and ethanol. All the complexes are hydrogen-bonded, except the cobalt complex [Co(HMTA) 2 (NO 3 ) 2 (H 2 O) 2 ] which is polymeric. These complexes have been characterized by elemental analyses, infrared and visible spectroscopy as well as conductivity. The results suggest octahedral coordination in which the central metal ion is bonded to aqua ligands and the HMTA is bonded to the aqua ligands through hydrogen-bonding. Antibacterial activities of the ligand and its complexes show that the ligand is active against 1 out of 10 tested bacteria species; the cobalt complexes [Co(H 2 O) 6 ](HMTA) 2 (NO 3 ) 2 . 4H 2 O , and [Co(HMTA) 2 (NO 3 ) 2 (H 2 O) 2 ] are the most active, showing activity against all the microorganisms. These cobalt complexes also show greater activity than the reference antibiotic gentamycin against Klebsiella pneumonia. Keywords: Hexamethylenetetamine; Antimicrobial; Mn(II); Co(II); Ni(II). ______________________________________________________________________________ INTRODUCTION The emergence of antibiotic resistant pathogens and the continuing emphasis on health care costs has provoked a renewed interest in the design and development of novel and cost-effective antimicrobial agents with increased biological activity against the resistant strains [1-6]. Strategies currently being explored to tackle this problem include the structural modification of existing antimicrobial drugs to which resistance has developed and the development of entirely new classes of antimicrobial agents that work on different target sites [1,2]. Broad empirical screening of chemical entities for antimicrobial activity represents an alternative strategy for the development of new antimicrobials [2].