Chloride salts of the antibacterial agent pazufloxacin: (H3O)2(Pzfx)5Cl7·10H2O and (Pzfx)Cl·1.75H2O·0.5C2H5OH.

Recrystallization of pazufloxacinium mesylate from HCl solutions yielded two previously unknown salts of pazufloxacin. These were characterized by X-ray diffraction and are bis(oxidanium) pentakis[(2S)-6-(1-azaniumylcyclopropyl)-7-fluoro-2-methyl-10-oxo-4-oxa-1-azatricyclo[7.3.1.05,13]trideca-5(13),6,8,11-tetraene-11-carboxylic acid] heptachloride decahydrate, 2H3O+·5C16H16FN2O4+·7Cl-·10H2O (1), and (2S)-6-(1-azaniumylcyclopropyl)-7-fluoro-2-methyl-10-oxo-4-oxa-1-azatricyclo[7.3.1.05,13]trideca-5(13),6,8,11-tetraene-11-carboxylic acid chloride ethanol hemisolvate 1.75-hydrate, C16H16FN2O4+·Cl-·0.5C2H6O·1.75H2O (2), which were obtained from acetonitrile and ethanol, respectively. The compounds crystallize in the noncentrosymmetric triclinic space group P1. Salt 1 contains five independent cations and seven chloride anions, while compound 2 contains eight independent cations and anions. In both, an intramolecular COOH...O=C hydrogen bond is present and the amino group is protonated. The cations, anions and solvent molecules form extensive hydrogen-bonded frameworks. In addition, in both structures, the cations are packed into infinite stacks via π-π interactions, with interplanar distances of approximately 3.2 Å.