Platinum(II) complexes with fluoroquinolones: Synthesis and characterization of unusual metal–piperazine chelates

The fluoroquinolones constitute an important class of synthetic antimicrobial agents. The interaction between these compounds and metallic cations has been investigated primarily with the goal of identifying the functional groups directly linked to the metal. Furthermore, there has been some additional work investigating the effect of metal ions upon antibacterial activity. The vast majority of the metallic complexes reported in the literature show coordination of the fluoroquinolone through the carboxylate and the carbonyl oxygen atoms. In this work, we report the synthesis and characterization of platinum(II) complexes with ciprofloxacin, levofloxacin, ofloxacin, sparfloxacin, and gatifloxacin. The resulting complexes present the fluoroquinolone coordinated through the nitrogen atoms of the piperazine ring, which is unusual. The proposed structures were supported by spectroscopic evidence (IR, NMR, and mass spectra) as well as by theoretical studies.