2-[3-(1H-Benzimidazol-2-yl)prop-yl]-1H-benzimidazol-3-ium 3,4,5-tri-hydroxy-benzoate trihydrate.

The characterized organic trihydrate title salt, C(17)H(17)N(4) (+)·C(7)H(5)O(5) (-)·3H(2)O or (HL)(+)(Gal)(-)·3H(2)O, with L = 1,3-bis-(1H-benzimidazol-2-yl)propane (C(17)H(16)N(4)) and HGal = 3,4,5-tri-hydroxy-benzoic acid (gallic acid, C(7)H(6)O(5)), crystallizes with two formulas per asymmetric unit. One-half of the cations in the crystal feature a bent shape, with the central propyl chain having a gauche conformation, and the other half is nearly linear, with a trans propyl chain. Both cations form two independent herringbone layers in the crystal, which allow efficient π-π inter-actions between aromatic rings of the benzimidazole moieties. These layers are parallel to (100), and anions and water mol-ecules of crystallization inter-calate between these cationic planes. All potential donor groups for hydrogen bonding (NH and OH groups) actually form hydrogen bonds, ensuring a good cohesion between layers of cations and anions, stacked along [100].