Crystal structure of 4,4'-bipyridine-1,1'-diium naphthalene-2,6-disulfonate dihydrate

The title hydrated molecular organic salt, C10H10N22+C10H6O6S22-2H2O, crystallized with half a bipyridinium cation, half a naphthalene-2,6-disulfonate anion and a water molecule in the asymmetric unit. The whole cation and anion are generated by inversion symmetry, the inversion centers being at the center of the bridging C - C bond of the cation, and at the center of the fused C - C bond of the naphthalene group of the anion. In the crystal, the anions and cations stack alternately along the a axis with ?-? interactions [inter-centroid distance = 3.491 (1) Å]. The anions are linked via O - O(sulfonate) hydrogen bonds involving two inversion-related water molecules, forming chains along [10-1]. These chains are bridged by bifurcated N - (O,O) hydrogen bonds, forming a three-dimensional framework structure. There are also C - O hydrogen bonds present, reinforcing the framework structure.