Crystal structure of ()-4-(3-carb-oxy-1-ethyl-6,8-di-fluoro-4-oxo-1,4-di-hydro-quinolin-7-yl)-2-methyl-piperazin-1-ium 3-carb-oxy-5-fluoro-benzoate.

In the title organic salt, CHFNO ·CHFO , proton transfer leads to one protonated lomefloxacin mol-ecule (HLf) and one 3-carb-oxy-5-fluoro-benzoate (5-F-Hip) anion in the asymmetric unit. The HLf cation is bent, with a dihedral angle of 38.3 (1)° between the quinoline ring and the piperazinium moiety. In the crystal, two kinds of N-H⋯O and O-H⋯O hydrogen-bonded chains cross-link each other to produce a three-dimensional network structure that is additionally stabilized by weak C-H⋯O and C-H⋯F hydrogen bonds, as well as π-π inter-actions. The methyl group attached to the piperazinium ring is disordered over two sets of sites [refined ratio: 0.645 (5):0.335 (5)], indicating the presence of both enanti-omers of the cation in the structure.