Hydrogen bonding in proton-transfer compounds of 5-sulfosalicylic acid with bicyclic heteroaromatic Lewis bases.

The crystal structures of quinolinium 3-carboxy-4-hydroxybenzenesulfonate trihydrate, C9H8N + C7H5O6S 3H2O, (I), 8-hydroxyquinolinium 3-carboxy-4-hydroxybenzenesulfonate monohydrate, C9H8NO + C7H5O6S H2O, (II), 8-aminoquinolinium 3-carboxy-4-hydroxybenzenesulfonate dihydrate, C9H9N2 + C7H5O6S 2H2O, (III), and 2-carboxyquinolinium 3-carboxy-4-hydroxybenzenesulfonate quinolinium-2-carboxylate, C10H8NO2 + C7H5O6S C10H7NO2, (IV), four protontransfer compounds of 5-sulfosalicylic acid with bicyclic heteroaromatic Lewis bases, reveal in each the presence of variously hydrogen-bonded polymers. In only one of these compounds, viz. (II), is the protonated quinolinium group involved in a direct primary NÐH O(sulfonate) hydrogenbonding interaction, while in the other hydrates, viz. (I) and (III), the water molecules participate in the primary intermediate interaction. The quinaldic acid (quinoline-2carboxylic acid) adduct, (IV), exhibits cation±cation and anion±adduct hydrogen bonding but no direct formal heteromolecular interaction other than a number of weak cation± anion and cation±adduct ± stacking associations. In all other compounds, secondary interactions give rise to network polymer structures.