Short Communication: 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

Abstract

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.

Manuscript received: 1 February 2001.