Molecular cocrystals of carboxylic acids:: the preparation of the 1:1 proton-transfer compounds of creatinine with a series of aromatic acids and the crystal structure of that with pyrazine-2,3-dicarboxylic acid

The 1:1 proton-transfer compounds of creatinine with a series of aromatic carboxylic acids have been prepared and characterized using infrared spectroscopy and in one case with single-crystal X-ray crystallography. The acids are the mononitro-substituted benzoic acids 3,5-dinitrobenzoic acid, 5-nitrosalicylic acid, 3, 5-dinitrosalicylic acid and pyrazine-2,3-dicarboxylic acid. The crystal structure of the compound with pyrazine-2,3-dicarboxylic acid, [(C4H8N3O+)(C6H3N2O4-)],shows a chain structure based on a primary asymmetric cyclic hydrogen-bonding dimer formed through the carboxylate group and the hetero-nitrogen of the acid, and the protonated imine and the adjacent hetero-amine proton of creatinine. Peripheral extension is through the second imine proton to the second carboxylic acid group of an adjacent acid molecule.