Crystallisation of 1,2-dimethylimidazole, and 1-methylimidazole with organic acids.

Crystals of 1-methylimidazole and 1,2-dimethylimidazole with glutaric and succinic acids are described. The crystal structure including 1,2-dimethylimidazole and glutaric acid, has been reported previously, but the molecular salt of 1-methylimidazole with succinic acid were characterized for the first time in this study. The structures were characterised by using X-ray crystallography, intermolecular hydrogen bond geometry, energy, and topology. In both crystal structures the molecules are linked by N-H….O and C-H….O hydrogen bonds. Using Hirshfeld surface analyses and quantum-theoretical calculations, we provide insights into the intermolecular interactions, revealing dependencies on the chemical environment. The result of the interaction region indicator (IRI) analysis indicated that succinic acid and 1-methylimidazole (II) exhibits low gradient, low density, and sharp spikes, whereas the spikes of the molecular salt of glutaric acid and 1,2-dimethylimidazole (I) are less dense. The quantum theory of atoms in molecules (QTAIM) analysis indicates that the described molecular salts exhibit different types of bond critical paths. These observations confirm the hydrogen bonded nature of molecular salts based on the characteristics of the bond critical points.