Cobalt(II) complexes of sparfloxacin: Characterization, structure, antimicrobial activity and interaction with DNA and albumins.

The cobalt(II) complexes with the quinolone sparfloxacin (Hsf) in the absence or presence of the nitrogen-donor heterocyclic ligands 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen) or 2,2'-bipyridylamine (bipyam) were prepared and characterized physicochemically and spectroscopically. The crystal structures of complexes [Co(sf)2(bipy)]∙3MeOH∙2H2O and [Co(sf)2(phen)]∙4MeOH were determined by X-ray crystallography. The antimicrobial activity of the complexes was tested against four different microorganisms (Escherichia coli, Xanthomonas campestris, Staphylococcus aureus and Bacillus subtilis) and was found similar or higher than that of free Hsf. The binding of the complexes to calf-thymus DNA was monitored by UV-vis spectroscopy and DNA-viscosity measurements and indirectly by competitive studies with ethidium bromide; intercalation is suggested as the most possible interaction mode. Fluorescence emission spectroscopy was used to evaluate the interaction of the complexes with human or bovine serum albumin and the corresponding binding constants were determined.