The squaric acid molecule: a hydrogen bond study of dimethylammonium hydrobis(hydrogen squarate)(H2NMe2)+[H3(C4O4)2]?

Abstract

The title compound has been synthesized and studied by X-ray diffraction methods. Crystals are orthorhombic, space group Pccn, with Z= 4 in a unit cell of dimensions: a= 6·080(3), b= 15·739(14), c= 11·883(9)Å. The structure was solved by direct methods and the final weighted discrepancy factor was 0·050, after anisotropic full-matrix least-squares refinement on 2369 unique reflections measured on a diffractometer. Strong intermolecular hydrogen bonding interactions, both symmetric [O O 2·435(2)Å] and asymmetric [O O 2·582(2)Å] exist between squaric acid molecules, two of which are linked via one hydrogen atom, with a dihedral angle 26·5° between two C₄O₄ planes.