Lomefloxacinium picrate.

IN THE CATION OF THE TITLE COMPOUND [SYSTEMATIC NAME: (RS)-4-(3-carb-oxy-1-ethyl-6,8-difluoro-4-oxo-1,4-dihydro-quinolin-7-yl)-2-methyl-piperazin-1-ium 2,4,6-trinitro-phenolate], C(17)H(20)F(2)N(3)O(3) (+)·C(6)H(2)N(3)O(7) (-), the piper-azine ring adopts a slightly distorted chair conformation and contains a protonated N atom. An intra-molecular O-H⋯O hydrogen bond occurs in the cation. The dihedral angles between the mean planes of the six-atom piperazine ring and the 10-atom fused ring system is 43.3 (5)°. The picrate anion inter-acts with the protonated N atom of an adjacent cation through a bifurcated N-H⋯(O,O) three-center hydrogen bond. Strong N-H⋯O hydrogen bonds in concert with weak π-π stacking inter-actions [centroid-centroid distance = 3.6460 (14) Å] dominate the crystal packing, creating a two-dimensional network structure along [011].