A monoclinic polymorph of 5-[(1H-benzimidazol-1-yl)methyl]benzene-1,3dicarboxylic acid

Crystals of the title compound, C16H12N2O4, were obtained accidentally by the hydrothermal reaction of 5-[(1H-benzo[d]imidazol-1-yl)methyl]isophthalic acid with manganese chloride tetrahydrate in the presence of KOH as alkaline reagent for the deprotonation. A triclinic polymorph of this structure has been reported previously from a similar reaction [Cheng (2011). Acta Cryst. E67, o3299]. The benzimidazole ring system is almost planar, with a maximum deviation from the mean plane of 0.020 (4) angstrom. The benzimidazole unit and benzene ring are inclined at a dihedral angle of 68.17 (4)degrees, reflecting the axial rotation of the flexible benzimidazolyl arm. In the crystal, pairs of O-H center dot center dot center dot O hydrogen bonds link adjacent molecules into inversion dimers. O-H center dot center dot center dot N contacts connect these dimers into zigzag chains along [010].