2-Methylpyridinium 2-carboxybenzoate–benzene-1,2-dicarboxylic acid (2/1)

Abstract

The asymmetric unit of the title compound, C6H8N+·C8H5O4−·0.5C8H6O4, contains a 2-methylpyridinium cation, a 2-carboxybenzoate monoanion and half of the co-crystallized benzene-1,2-dicarboxylic acid molecule, which lies on a mirror plane. The N atom of the pyridine ring is protonated, while the anion of this salt is generated by deprotonation of the OH group of one of the carboxylic acid substituents of the benzene-1,2-dicarboxylic acid molecule. The pyridine ring of the cation is inclined to the benzene ring of the anion at an angle of 2.27 (11)°. The benzene ring of the anion makes dihedral angles of 2.8 (2) and 6.0 (2)° with the carboxylate and carboxyl substituents, respectively. An intramolecular O—H...O hydrogen bond in the anion closes anS(7) ring. In the crystal, weak N—H...O, O—H...O and C—H...O hydrogen bonds lead to the formation of a three-dimensional network. Weak offset π–π contacts [centroid-to-centroid distance = 3.852 (1) Å] are also observed.