2,3-Dimethyl-1-imidazol-3-ium benzene-sulfonate-1,2-dimethyl-1-imidazole co-crystal.

In the title co-crystal, CHN ·CHOS·CHN, the two 1,2-di-methyl-imidazole rings exist as partially protonated moieties in the asymmetric unit as a two-part disordered unit wherein the acidic hydrogen atom is bound to each ring. The two imidazolium cations share a strong hydrogen bond the acidic hydrogen atom, which is disordered between two positions, being bonded to the first second imidazole ring in a 0.33 (2) to 0.67 (2) ratio. A benzene sulfonate anion is present for charge balance and inter-acts with the aromatic H atoms on both imidazole rings as well as with the methyl groups on the rings.