The Influence by Substituents on the Intermolecular Hydrogen-Bonding Interactions in Imidazole-4,5-dicarboxylic Acid Derivatives

A series of chiral imidazole-4,5-dicarboxylic acid derivatives was prepared in order to test the significance that
stereochemistry and substitution have on the preferred intermolecular associations of the compounds in solution and the solid state.
Solution 1H NMR spectroscopy provided evidence for racemic associations by enantiomeric imidazole-4,5-dicarboxamides (I45DCs)
but not for enantiomeric imidazole-4-carboxylic acid ester-5-carboxamides (I45EAs). Melting point phase diagrams illustrate that
enantiomeric and dissymmetrically disubstituted imidazole-4,5-dicarboxamides (I45DCs) preferably form racemic compounds in
the solid state. It is anticipated that the aggregation occurs through intermolecular hydrogen-bonding interactions identified for
similar compounds in this class. In contrast, imidazole-4-carboxylic acid ester-5-carboxamides (I45EAs) form intermolecular hydrogen-bonded tapes, and equimolar mixtures of enantiomeric I45EAs yield solid solutions.