Crystal structure of 4,4'-bipyridine-1,1'-diium naphthalene-2,6-di-sulfonate dihydrate.

The title hydrated mol-ecular organic salt, C10H10N2 (2+)·C10H6O6S2 (2-)·2H2O, crystallized with half a bipyridinium cation, half a naphthalene-2,6-di-sulfonate anion and a water mol-ecule 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 π-π inter-actions [inter-centroid distance = 3.491 (1) Å]. The anions are linked via O-H⋯O(sulfonate) hydrogen bonds involving two inversion-related water mol-ecules, forming chains along [10-1]. These chains are bridged by bifurcated N-H⋯(O,O) hydrogen bonds, forming a three-dimensional framework structure. There are also C-H⋯O hydrogen bonds present, reinforcing the framework structure.