2-[3-(1<i>H</i>-Benzimidazol-2-yl)propyl]-1<i>H</i>-benzimidazol-3-ium 3,4,5-trihydroxybenzoate trihydrate

The characterized organic trihydrate title salt, C₁₇H₁₇N₄ ⁺·C₇H₅O₅ ^-·3H₂O or (H<i>L</i>)⁺(Gal)^-·3H₂O, with <i>L</i> = 1,3-bis-(1<i>H</i>-benzimidazol-2-yl)propane (C₁₇H₁₆N₄) and HGal = 3,4,5-tri-hydroxy-benzoic acid (gallic acid, C₇H₆O₅), 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 <i>gauche</i> conformation, and the other half is nearly linear, with a <i>trans</i> 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].