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Template synthesis and characterization of biologically active transition metal complexes comprising 14-membered tetraazamacrocyclic ligand

Singh Dharmpal (Department of Chemistry, National Institute of Technology, Kurukshetra, India)
Kumar Krishan (Department of Chemistry, National Institute of Technology, Kurukshetra, India)
Kumar Ramesh (Department of Chemistry, National Institute of Technology, Kurukshetra, India)
Singh Jitender (D.M. Division, National Dairy Research Institute, Karnal, India)

A novel series of complexes of the type [M(C28H24N4)X2], where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), X = Cl-, NO3 -, CH3COO- and (C28H24N4) corresponds to the tetradentate macrocyclic ligand, were synthesized by template condensation of 1,8-diaminonaphthalene and diacetyl in the presence of divalent metal salts in methanolic medium. The complexes were characterized by elemental analyses, conductance and magnetic measurements, as well as by UV/Vis, NMR, IR and MS spectroscopy. The low values of the molar conductance indicate non-electrolyte type of complexes. Based on these spectral data, a distorted octahedral geometry may be proposed for all of these complexes. All the synthesized macrocyclic complexes were tested for in vitro antibacterial activity against some pathogenic bacterial strains, viz Bacillus cereus, Salmonella typhi, Escherichia coli and Staphylococcus aureus. The MIC values shown by the complexes against these bacterial strains were compared with the MIC shown by the standard antibiotics linezolid and cefaclor.

Keywords: antibacterial activity, diaminonaphthalene, macrocyclic complexes, spectroscopic studies