The Origin of Bulk Polarity in Hydrogensulfate Salts

Bis(1,2,3-benzotriazolium) sulfate dihydrate

In the asymmetric unit of the title hydrated salt, 2C₆H₆N₃⁺·SO₄²⁻·2H₂O, there are two independent sulfate ions, one lying on a twofold axis, and the other in a general position. There are three independent benzotriazolium cations and three independent water mol­ecules. The sulfate ion in a general position forms hydrogen-bonded chains of stoichiometry SO₄²⁻·3H₂O in the b-axis direction. The sulfate on the twofold axis is unhydrated and accepts hydrogen bonds from four surrounding benzotriazoles. The benzotriazolium cations form two types of stacks along b. One stack contains only one type of independent cation, related by inversion centers. The other stack contains two alternating independent cations and no symmetry. The two types of stacks have orientations which are rotated by about 79° in the ac plane. 12 symmetrically distinct hydrogen bonds of type N—H⋯O(sulfate), N—H⋯O(water), O—H⋯O(sulfate) and O—H⋯O(water), with donor–acceptor distances in the range 2.5490 (13)–2.7871 (12) Å, form a three-dimensional array.