Mixed ligand cobalt complexes of lincomycin with diimine ligands: Synthesis, spectroscopic and biological investigation

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Abstract

Four new mixed ligand cobalt complexes with the antibiotic lincomycin and diimine ligands have been synthesized by reacting lincomycin with suitable precursor complexes to obtain [Cobpy2Lin]Cl2.8H2O (1), [Cobpy2Lin]Cl3 (2), [Cophen2Lin]Cl3 (3), [Copd2Lin]Cl3 (4) in good yield. These complexes were characterized by their electronic spectra. Antibacterial susceptibility tests of these complexes against five test isolates showed that two of these complexes (2 and 3) possess improved antibacterial activity or have activities in the same range with lincomycin, the parent antibiotic. Ethidium bromide fluorescence quenching experiment of complex 3 resulted in slight decrease in the emission intensity of CT DNA-bound ethidium bromide due to partial intercalation of the complex into CT DNA. The partial intercalation of the complex 3 was due to the planar phenanthroline ligand moiety and the weak interaction with DNA was caused by the bulky ancillary lincomycin ligand. This substantiates the weak antibacterial activity of the complex and that of the other complexes as the complexes can only bind to the DNA of the test organisms weakly

Keywords: antimicrobial, cobalt, diimine, lincomycin, spectroscopy

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