Crystal structure of 4-chloro-2-nitro-benzoic acid with 4-hy-droxy-quinoline: a disordered structure over two states of 4-chloro-2-nitro-benzoic acid-quinolin-4(1)-one (1/1) and 4-hy-droxy-quinolinium 4-chloro-2-nitro-benzoate.

The title compound, CHNO·CHClNO, was analysed as a disordered structure over two states, . co-crystal and salt, accompanied by a keto-enol tautomerization in the base mol-ecule. The co-crystal is 4-chloro-2-nitro-benzoic acid-quinolin-4(1)-one (1/1), CHClNO·CHNO, and the salt is 4-hy-droxy-quinolinium 4-chloro-2-nitro-benzoate, CHNO·CHClNO . In the compound, the acid and base mol-ecules are held together by a short hydrogen bond [O⋯O = 2.4393 (15) Å], in which the H atom is disordered over two positions with equal occupancies. In the crystal, the hydrogen-bonded acid-base units are linked by N-H⋯O and C-H⋯O hydrogen bonds, forming a tape structure along the axis direction. The tapes are stacked into a layer parallel to the plane π-π inter-actions [centroid-centroid distances = 3.5504 (8)-3.9010 (11) Å]. The layers are further linked by another C-H⋯O hydrogen bond, forming a three-dimensional network. Hirshfeld surfaces for the title compound mapped over shape-index and were generated to visualize the inter-molecular inter-actions.