New type of saccharinate crystals: A possible supramolecular synthon

Saccharin forms robust synthons with pyridine derivatives. A new 3-ring synthon has been found for saccharin and 2,2′-bpy derivatives at 2:1 M (molar) ratio. The acidic proton of saccharin is transferred to one of the 2,2′-bpy N-atoms and becomes located in central region of the 3 N-atoms in structure. The new synthon gives an opportunity for supramolecular construction that locks the 2,2′-bpy in cis conformation. As an acid, saccharin neutralizes 2,2′-bpy derivatives to give structures with a locked cis 2,2′-bpy skeleton, consistent to the known increasing solubility of 2,2′-bpy derivatives using saccharin to form salts. To the best of our knowledge, this is also one of the very rare times to have observed that ionic and neutral forms of saccharin coexist simultaneously in the solid state.