Supramolecular Assemblies in Salts of 2,2＇-Biimidazole with 5-Sulfosalicylic Acid and 3,4,5-Trihydroxybenzoic Acid

Supramolecular assemblies of 2,2＇-biimidazole with 5-sulfosalicylic acid and 3,4,5-trihydroxybenzoic acid, have been synthesized and characterized by single-crystal X-ray diffraction methods. Both the two proton-transfer compounds of 2,2＇-biimidazole with 3-carboxy-4-hydroxybenzenesulfonic acid （5-sulfosalicylic acid, 5-SSA） [namely bis（2-（2-1H-imidazolyl）-1H-imidazolium） 4-hydroxybenzene-3-carboxylate-1-sulfonate monohydrate, 2（C6HTN4）^＋· CTH4068^2-.H2O, （Ⅰ）] and 3,4,5-trihydroxybenzoic acid [namely 2,2＇-bi-1H-imidazolium bis（3,4,5-trihydroxybenzoate） tetrahydrate, C6H8N4^2＋ ·2（C7H5O5）^-·4（H20）, （Ⅱ）] feature extensively hydrogen-bonded three-dimensional network structures having significant interlayer n-n interactions between the cation and anion species. In Ⅰ, a 5-SSA^2- dianionic species results from deprotonation of both the sulfonic and the carboxylic acid groups, all available O-atom acceptors interact with all cation and water molecule donors by hydrogen bonds. In Ⅱ, the formula unit displays a crystallographic inversion symmetry. The structural information about the two complexes between 2,2＇-biimidazole compound and benzenecarboxylic acids obtained in this work will be particularly important for the rational design of supramolecular organic functional materials.