Ribbons of hydrogen-bonded rings in the 1:2 complex of pyromellitic acid and dimethyl sulfoxide.

In the title complex, pyromellitic acid-dimethyl sulfoxide (1/2), C(10)H(6)O(8).2C(2)H(6)OS, molecules of pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid) and dimethyl sulfoxide, the latter being well ordered, are linked to each other by O-H.O hydrogen bonds. The formula unit displays crystallographic inversion symmetry. The packing consists of ribbons of hydrogen-bonded rings that can be described by graph set C(2)(1)(10)R(4)(2)(18).