Redetermination of tetra-methyl tetra-thia-fulvalene-2,3,6,7-tetra-carboxyl-ate

5,5′-(Ethyne-1,2-diyl)diisophthalic acid dimethyl sulfoxide tetrasolvate

In the title compound, C₁₈H₁₀O₈·4C₂H₆OS, the mid-point of the triple bond of the main mol­ecule is located on a special position, i.e. about an inversion center. The carboxyl groups are twisted slightly out of the planes of the aromatic rings to which they are attached, making dihedral angles of 24.89 (1) and 7.40 (2)°. The cystal packing features strong O—H⋯O hydrogen bonds, weaker C—H⋯O inter­actions and O⋯S contacts [3.0981 (11) Å] and displays channel-like voids extending along the a-axis direction which contain the dimethyl sulfoxide solvent mol­ecules.