Benzoic acid-2,2'-biimidazole (2/1).

In the title compound, C(6)H(6)N(4)·2C(7)H(6)O(2), the asymmetric unit contains a half-mol-ecule of biimidazole and one benzoic acid mol-ecule. The unit cell contains two biimidazole mol-ecules and four benzoic acid mol-ecules, giving the reported 2:1 ratio of benzoic acid to biimidazole. The biimidazole mol-ecule is located on an inversion center (passing through the central C-C bond). Strong N-H⋯O and O-H⋯N hydrogen bonds link the benzoic acid mol-ecules with the neutral biimidazole mol-ecules, which lie in planar sheets. In the crystal packing, the parallel sheets are related by a twofold rotation axis and an inversion centre, respectively, forming an inter-woven three-dimensional network via weak C=O⋯π inter-molecular inter-actions between neighboring mol-ecules.