Enrofloxacinium picrate.

There is one cation-anion pair in the asymmetric unit of the title compound [systematic name: 4-(3-carb-oxy-6-fluoro-4-oxo-1,4-dihydroquinolin-7-yl)-1-ethyl-piperazin-1-ium 2,4,6-tri-nitro-phenolate], C(19)H(23)FN(3)O(3) (+)·C(6)H(2)N(3)O(7) (-). The six-membered piperazine group in the cation adopts a slightly distorted chair conformation and contains a protonated N atom. The dihedral angles between the mean planes of the cyclo-propyl and piperazine rings in the cation with the 10-atom ring system of the quinolone group are 48.1 (1) and 69.9 (5)°, respectively. The picrate anion inter-acts with the protonated N atom of an adjacent cation through a bifurcated N-H⋯O three-center hydrogen bond, forming an R(1) (2)(6) ring motif. Furthermore, there is an intra-molecular O-H⋯O hydrogen bond. The dihedral angle between the mean planes of the anion benzene and cation piperizine, quinoline and cyclo-propyl rings are 61.3 (6), 31.1 (4) and 70.4 (9)°, respectively. The mean planes of the two o-NO(2) and single p-NO(2) groups in the picrate anion are twisted by 6.7 (6), 38.3 (9) and 12.8 (7)° with respect to the mean plane of the benzene ring. Strong N-H⋯O and weak inter-molecular C-H⋯O hydrogen bonds in concert with weak π-π stacking inter-actions [centroid-centroid distances = 3.5785 (13), 3.7451 (12) and 3.6587 (13) Å] dominate the crystal packing.