X-ray crystal structures of two solvent complexes involving positionally isomeric 9,10-anthraquinonecarboxylic acids and DMSO

Two constitutionally isomeric 9,10-anthraquinonecarboxylic acids 1 and 2 are reported to yield DMSO-solvated crystals (1a and 2a) on the crystallization from DMSO. The molecular and crystal structures are described and comparatively discussed with reference to the effect implicated by the different position of the carboxylic group at the anthraquinone basis and the involvement of the solvent molecule.