Synthesis, Characterization and Antibacterial Studies of Benzylpenicillin and its Co(II) Complex

Abstract

Co(II) complex of benzylpenicillin was synthesized by the reaction between benzylpenicillin and CoCl₂.6H₂O. The structure and nature of bonding of the complex have been explored by conductivity, elemental analysis, continuous variation method, infrared and UV-Visible spectroscopy. The physical properties such as colour, solubility and melting point were determined for both the benzylpenicillin and its Co(II) complex. Elemental analysis of the complex agreed with the calculated value. Continuous variation method suggested metal:ligand ratio of 1:1. From the spectral data analysis, the ligand benzylpenicillin behaved as a tetradentate ligand coordinating to the metal ion through OH, C=O of amide, C=O of carboxylate, C=O of β-lactam and NH. A trigonal bipyramidal geometry has been proposed for the metal complex. Benzylpenicillin and its Co(II) complex have been screened for their in vitro antibacterial activity against four gram positive strains (Staphyloccocus aureus, Bacillus subtilis, Bacillus cereus and Enterococcus feacalis) and four gram negative (Escherichia coli, Enterobacter clocae, Pseudomonas aeruginosa and Campylobacter fetus). The Co(II) complex showed enhanced antibacterial activity when compared with pure benzylpenicillin. It was deduced that Co(II) benzylpenicillin complex have improved antibacterial activity than benzylpencillin alone and it was evident that the overall potency of benzylpencillin was enhanced on coordination with cobalt ion.

Keywords: Antibacterial, Benzylpenicillin, Complex, Tetradentate, Co(II)