Synthesis, Characterization and Biological Profile of Cationic Cobalt Complexes with First-Generation Quinolones

The interaction of cobalt(II) with first-generation quinolones oxolinic acid (Hoxo), flumequine (Hflmq), pipemidic acid (Hppa) and cinoxacin (Hcx) in the presence of the <i>N</i>,<i>N'</i>-donor heterocyclic ligands 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen) afforded a series of novel cobalt complexes, namely [Co(bipy)₂(oxo)](PF₆)₂·H₂O (<b>1</b>), [Co(phen)₂(oxo)](PF₆)₂·0.5CH₃OH·0.5H₂O (<b>2</b>), [Co(bipy)₂(flmq)](PF₆)₂·0.5CH₃OH·0.5H₂O (<b>3</b>), [Co(bipy)₂(ppa)](PF₆)₂·CH₃OH·0.5H₂O (<b>4</b>), [Co(phen)₂(cx)](PF₆)₂·CH₃OH·0.5H₂O (<b>5</b>), and [Co(phen)₂(flmq)](PF₆)·0.5CH₃OH·H₂O (<b>6</b>). The characterization of the complexes involved physicochemical techniques, various spectroscopies and single-crystal X-ray crystallography. The affinity of complexes to calf-thymus (CT) DNA was monitored with various techniques, suggesting intercalation in-between the DNA-nucleobases as the most probable interaction mode, which may be combined with electrostatic interactions as a result of the cationic nature of the complexes. The affinity of the complexes for bovine and human serum albumin proteins was monitored, and the determined corresponding albumin-binding constants revealed a tight and reversible interaction.