1,4,5,8-Naphthalenetetracarboxylic Acid Cyclic 1,8-Anhydride Bis(dimethyl sulfoxide) Solvate and 1,4,5,8-Naphthalenetetracarboxylic 1,8:4,5-Dianhydride

1,4,5,8-Naphthalenetetracarboxylic acid cyclic 1,8-anhydride crystallized from dimethyl sulfoxide (DMSO) as the solvate, C₁₄H₆O₇.2C₂H₆OS, in the centrosymmetric space group P. Two O-H...O hydrogen bonds with O...O distances 2.592 (3) and 2.598 (3) Å are formed with the two carboxylic acid OH groups as donors and the O atoms of the two inequivalent DMSO molecules as acceptors. The carboxylic H atoms are ordered, as are the carboxylic O atoms. In addition to the conventional hydrogen bonds there are numerous C—H...O interactions consistent with the large number of potential CH donors and O-atom acceptors. 1,4,5,8-Naphthalenetetracarboxylic 1,8:4,5-dianhydride, C₁₄H₄O₆, crystallized in the centrosymmetric space group P2₁/c with half the molecule as the asymmetric unit. Each molecule is involved in four significant C—H...O interactions as a donor and in an additional four as an acceptor. These eight interactions link each mol­ecule to six neighboring mol­ecules, forming a three-dimensional network. Geometric parameters of both substances are in general agreement with analogous parameters for naphthalic anhydride, monosodium 1,4,5,8-naphthalenetetracarboxylic acid cyclic 1,8-anhydride monohydrate and 1,4,5,8-naphthalenetetracarboxylic 1,8:4,5-dianhydride as reported previously.

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