Crystal structures of 3-chloro-2-nitro-benzoic acid with quinoline derivatives: 3-chloro-2-nitro-benzoic acid-5-nitro-quinoline (1/1), 3-chloro-2-nitro-benzoic acid-6-nitro-quinoline (1/1) and 8-hy-droxy-quinolinium 3-chloro-2-nitro-benzoate.

The structures of three compounds of 3-chloro-2-nitro-benzoic acid with 5-nitro-quinoline, (I), 6-nitro-quinoline, (II), and 8-hy-droxy-quinoline, (III), have been determined at 190 K. In each of the two isomeric compounds, (I) and (II), C7 H4 ClNO4 ·C9 H6 N2 O2 , the acid and base mol-ecules are held together by O-H⋯N and C-H⋯O hydrogen bonds. In compound (III), C9 H8 NO+ ·C7 H3 ClNO4 - , an acid-base inter-action involving H-atom transfer occurs and the H atom is located at the N site of the base mol-ecule. In the crystal of (I), the hydrogen-bonded acid-base units are linked by C-H⋯O hydrogen bonds, forming a tape structure along the b- axis direction. Adjacent tapes, which are related by a twofold rotation axis, are linked by a third C-H⋯O hydrogen bond, forming wide ribbons parallel to the (03) plane. These ribbons are stacked via π-π inter-actions between the quinoline ring systems [centroid-centroid distances = 3.4935 (5)-3.7721 (6) Å], forming layers parallel to the ab plane. In the crystal of (II), the hydrogen-bonded acid-base units are also linked into a tape structure along the b- axis direction via C-H⋯O hydrogen bonds. Inversion-related tapes are linked by further C-H⋯O hydrogen bonds to form wide ribbons parallel to the (08) plane. The ribbons are linked by weak π-π inter-actions [centroid-centroid distances = 3.8016 (8)-3.9247 (9) Å], forming a three-dimensional structure. In the crystal of (III), the cations and the anions are alternately linked via N-H⋯O and O-H⋯O hydrogen bonds, forming a 21 helix running along the b- axis direction. The cations and the anions are further stacked alternately in columns along the a- axis direction via π-π inter-actions [centroid-centroid distances = 3.8016 (8)-3.9247 (9) Å], and the mol-ecular chains are linked into layers parallel to the ab plane through these inter-actions.