Bis{4-[(Z)-N′-(4-hydroxybenzylidene)hydrazino]-8-(trifluoromethyl)quinolinium} sulfate dihydrate

The title compound, 2C17H13F3N3O+·SO4 2−·2H2O, crystallizes with four independent cations (A, B, C and D) in the asymmetric unit, which is composed of two groups of two cations, one anion and two water molecules (Z′ = 2). The dihedral angle between the mean planes of the 4-hydroxyphenyl and quinolinium groups is 8.9 (7)° in A, 30.1 (6)° in B, 28.8 (8)° in C and 12.8 (1)° in D. The crystal packing is stabilized by intermolecular O—H⋯O and N—H⋯O hydrogen bonding between H atoms from 4-hydroxyphenyl O atoms and the O atoms of nearby water molecules and sulfate anions, as well as H atoms from the N atom of the hydrazino group to O atoms of neighboring sulfate anions, linking the components into chains with the 4-hydroxyphenyl and quinolinium rings parallel to the (011) plane. There is also an extensive array of intermolecular hydrogen bonds between water molecules themselves and with sulfate O atoms, as well as hydrogen-bond interactions between H atoms from the hydrazino group and sulfate O atoms. In addition, intermolecular π–π stacking interactions occur between nearby 4-hydroxyphenyl and quinolinium groups, with distances between the centroids of interacting rings in the range 3.4140 (9)–3.9659 (9) Å.