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Synthesis, Spectroscopic Characterization, Antimicrobial and Antioxidant Properties of Some Metal(II) Complexes of Mixed Ligands-Riboflavin and 4-Aminobenzoic Acid

Agbaje OBA, Osowole AA,Malumi EO and Wakil SM

Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of mixed ligands, Riboflavin (HL) and 4-aminobenzoic acid (HL1) were synthesized and characterized by percentage metal, infrared and electronic (solid reflectance) spectroscopies, room temperature magnetic moments, melting points and conductance measurements. The conductance measurements in DMSO and percentage metal analysis indicated that all the metal(II) complexes were covalent and analyzed as [M(HL)(HL1)X].aH O, where X = Cl /SO . Infrared spectra data confirmed that coordination was via the 2 4oxygen atoms of two hydroxyl groups in Riboflavin, and the carboxylate oxygen atoms in 4-aminobenzoic acid respectively. Furthermore, electronic spectra data indicated that all the metal(II) complexes adopted octahedral geometry, while room temperature magnetic moment measurements indicated spin-crossover, that is, high spin low spinoctahedral equilibrium forall the complexes with the exceptions of the Cu(II) and Zn(II) complexes. In-vitro antimicrobial activities of the metal(II)complexes, riboflavin and p-aminobenzoic acid against Escherichia spp, Proteus mirabilis, Streptococcus pyogenes, Candida albicans, Salmonella sp, Streptococcus sp, Bacillus spp, Staphylococcus sp and Pseudomonas spp revealed that all the metal(II) complexes and ligands were active against Pseudomonas sp with inhibitory zones range of 7.0-11.0 mm. The antioxidant studies on the metal complexes showed that the Zn(II) complex had the best antioxidant activity of about 62 percentage inhibition, which was about twice the percentage inhibition ofthe standards, ascorbic acid and D-tocopherol.