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

The title hydrated mol­ecular organic salt, C(10)H(10)N(2) (2+)·C(10)H(6)O(6)S(2) (2−)·2H(2)O, 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 π–π inter­actions [inter-centroid distance = 3.491 (1) Å]. The anions are linked via O—H⋯O(sulfonate) hydrogen bonds involving two inversion-related water mol­ecules, 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.