Three-dimensional Networks

Abstract

The two title compounds of 2,2'-biimidazole (Bim) with 5-sulfosalicylic acid (5-H2SSA) and 2,2'-bibenzimidazole (Bbim) with 5-H2SSA are 1:2 organic salts, viz. C6H8N42+.2C7H5O6S-, (I), and C14H12N42+.2C7H5O6S-.3H2O, (II). The cation of compound (I) lies on a centre of inversion, whereas that of (II) lies on a twofold axis. Whilst compound (I) is anhydrous, three water molecules are incorporated into the crystal structure of (II). The substitution of imidazole H atoms by other chemical groups may favour the incorporation of water molecules into the crystal structure. In both compounds, the component cations and anions adopt a homogeneous arrangement, forming alternating cation and anion layers which run parallel to the (001) plane in (I) and to the (100) plane in (II). By a combination of N-H...O, O-H...O and C-H...O hydrogen bonds, the ions in both compounds are linked into three-dimensional networks. In addition, [pi]-[pi] interactions are observed between symmetry-related benzene rings of Bbim2+ cations in (II).