2-[3-(1 H-Benzimidazol-2-yl)prop-yl]-1 H-benzimidazol-3-ium 3,4,5-tri-hydroxy-benzoate-1,3-bis-(1 H-benzimidazol-2-yl)propane-ethyl acetate (2/1/2.94): co-crystallization between a salt, a neutral mol-ecule and a solvent

Abstract

The chemical formula of the title compound, 2C₁₇H₁₇N₄ ⁺·2C₇H₅O₅ ^-·C₁₇H₁₆N₄·2.94C₄H₈O₂, was established by X-ray diffraction of a single-crystal obtained by reacting 1,3-bis-(benzimidazol-2-yl)propane (L) and gallic acid (HGal) in ethyl acetate. The mol-ecular structure can be described as a salt (HL)⁺(Gal)^- co-crystallized with a mol-ecule L, with a stoichiometric relation of 2:1. Moreover, large voids in the crystal are filled with ethyl acetate, the amount of which was estimated by using a solvent mask during structure refinement, affording the chemical formula (HL ⁺·Gal^-)₂·L·(C₄H₈O₂)_2.94. The arrangement of components in the crystal is driven by O-H⋯O, N-H⋯O and O-H⋯N hydrogen bonds rather than by π-π or C-H⋯π inter-actions. In the crystal, mol-ecules and ions shape the boundary of cylindrical tunnels parallel to [100] via R (rings) and D (discrete) supra-molecular motifs. These voids, which account for about 28% of the unit-cell volume, contain disordered solvent mol-ecules.

Keywords: co-crystal; crystal structure; hydrogen bonds; solvent mask; supra­molecular structure.