aniline (1/1)

R factor = 0.047; wR factor = 0.118; data-to-parameter ratio = 14.7. Four independent molecules comprise the asymmetric unit of the title co-crystal, C10H9N3C7H5NO4, two for each compo-nent. Small conformational differences are noted for the benzoic acid derivatives, notably in the twists of the carboxylic acid residue out of the plane of the benzene ring to which it is connected [torsion angles = 167.62 (17) and 174.54 (17)]. In the aniline derivative, the major difference is observed in the dihedral angles formed between the CN3 and phenyl least-squares planes [1.51 (5) and 6.25 (6)]. Pairs of molecules associate via O—H N and N—H O hydrogen bonds leading to eight-membered { HOCO HNCN} hetero-synthons. The two-molecule aggregates are consolidated in the crystal structure by C—H O(nitro) and – interactions [shortest centroid–centroid distance between benzene rings = 3.6242 (10) Å]. Related literature For related studies in co-crystal formation, see: Wardell & Tiekink (2011). For the structure of N-(pyrimidin-2-yl)aniline, see: Badaruddin et al. (2009). For the structure of 4-nitro-benzoic acid, see: Tonogaki et al. (1993)