Hydrogen bonding and C-H...O interactions in bis(8-dimethylamino-1-dimethylammonionaphthalene) [(DMANH+)2] 4,8-dicarboxynaphthalene-1,5-dicarboxylate dihydrate

The title substance, 2C14H19N2+.C14H6O8(2-).2H2O, crystallized in the centrosymmetric space group P1 with one monopositive dimethylamine-dimethylammonio cation, half of a dinegative acid anion and one water molecule in the asymmetric unit, with the anion located on a center of symmetry. There are four intermolecular hydrogen bonds, of which three have Odonor...Oacceptor distances of 2.577 (1), 2.946 (2) and 2.764 (2) A, while the fourth has an Ndonor...Oacceptor distance of 3.154 (2) A. There is a single intramolecular hydrogen bond, in which the Ndonor...Nacceptor distance is 2.620 (2) A. In each case, the O, or N, and H atoms are ordered. The Ndonor-H distance in the intramolecular hydrogen bond, 1.06 (1) A, is among the shortest seen in this cation at room temperature. Moreover, the antiplanar orientation of the H atom in the hydrogen bond between acid anions is noteworthy. There are, in addition, 12 significant intermolecular C-H...O interactions. In these, the C...O distances range from 3.229 (2)-3.671 (2) A, while the C-H...O angles range from 121-165 degrees for the fixed H atoms involved. A three-dimensional network of hydrogen-bonding interactions is generated.