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Synthesis, Spectroscopic and Antibacterial Properties of Some Metal (II) Mixed Ligand Complexes of Riboflavin and 2,2?-Bipyridine.

Aderoju A Osowole, Anthony C Ekennia, and Austin E Osukwe

Mixed ligand complexes of Riboflavin (L) and 2,2’-Bipyridine (L1) with Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) ions were synthesized and characterized by, infrared and electronic spectroscopies, room temperature magnetic moments, melting points and conductance measurements. The % metal analysis confirmed that the complexes analyzed as [MX2(L)(L1)] where X = Cl/(CH3CO2)/SO4. Infrared spectra data confirmed that coordination is via the imine nitrogen and carbonyl oxygen atoms of the riboflavin, and the nitrogen atoms of the 2,2’-bipyridine molecules respectively. The room temperature magnetic moment and electronic spectra data indicated that all the metal(II) complexes were octahedral, and the Mn(II), Fe(II), Co(II) and Ni(II) complexes showed high spin low spin octahedral equilibrium. The conductance measurements of all the metal(II) complexes in water and DMSO showed that the complexes were all covalent. Interestingly, the in-vitro antibacterial studies of these metal(II) complexes, riboflavin and 2,2’-bipyridine against Bacillus cereus, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Klebsiella oxytoca and Staphylococcus aureus showed that none of the bacteria was sensitive to the former two compounds, with the exception of Proteus mirabilis which had activities of 20.0 mm and 13.0 mm against the Cu(II) complex and riboflavin. In contrast, all the bacteria were sensitive to 2, 2’-bipyridine, just like Augmentine, although with higher inhibitory zones range of 24.0-47.0 mm proving its potential as a broad spectrum antibacterial agent.