Stoichiometric and polymorphic salt of imidazolium picrate monohydrate

Abstract

The asymmetric unit of the title co-crystal salt, 1H-imidazol-3-ium 2,4,6-tri-nitro-phenolate monohydrate, C₄H₇N₂⁺·C₆H₂N₃O₇^-·H₂O, contains one imidazolium cation, one picrate anion and one solvent water mol-ecule of crystallization. The phenolic proton has been transferred to an imidazole N atom. In the crystal, the components are linked by N-H⋯O and O-H⋯O hydrogen bonds into a three-dimensional network which is further consolidated by weak C-H⋯O hydrogen bonds. In addition, π-π stacking inter-actions occur between pairs of imidazolium cations and picrate anions. If only the classical N-H⋯O and O-H⋯O hydrogen bonds are considered, the component ions are linked into a three-dimensional threefold inter-penetrating network of the topological type utp [or (10,3)-d]. Hirshfeld surface analysis indicates the crystal structure is mainly stabilized by H⋯·O contacts of the hydrogen bonds.

Keywords: co-crystal salt; crystal structure; imidazole; picric acid.

Figure 1

The morphologies of the two mol­ecular salts: needle (a) of (I) and block (b) of the crystal structure reported by Moreno-Fuquen et al. (2011 ▸).

Figure 2

Mol­ecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 3

Part of the crystal structure of (I), showing (a) the formation of the three-dimensional hydrogen-bonded network by N—H⋯O and O—H⋯O hydrogen bonds as dashed lines, (b) the simplified network when picrate, water and imidazolium ions are considered as 3-, 3- and 2-connected nodes, respectively, and (c) the simplified utp network.

Figure 4

Fingerprint plots of co-crystal salt (I) showing the percentage of the O⋯H and C⋯C contacts around the environment of picrate and imidazolium ions.