Crystal structures of the two salts 2-methyl-1H-imidazol-3-ium nitrate–2-methyl-1H-imidazole (1/1) and 2-methyl-1H-imidazol-3-ium nitrate

Abstract

The title salts, C4H7N2+·NO3−·C4H6N2, (I), and C4H7N2+·NO3−, (II), were obtained from solutions containing 2-methylimidazole and nitric acid in different concentrations. In the crystal structure of salt (I), one of the –NH H atoms of the imidazole ring shows half-occupancy, hence only every second molecule is in its cationic form. The nitrate anion in this structure lies on a twofold rotation axis. The neutral 2-methylimidazole molecule and the 2-methyl-1H-imidazol-3-ium cation interact through N—H...N hydrogen bonds to form [(C4H6N2)...(C4H7N2)+] pairs. These pairs are linked with two nitrate anions on both sides through bifurcated N—H...(O,O) hydrogen bonds into chains running parallel to [001]. In the crystal structure of salt (II), the C4H7N2+cation and the NO3−anion are both located on a mirror plane, leading to a statistical disorder of the methyl H atoms. The cations and anions again interact through bifurcated N—H...(O,O) hydrogen bonds, giving rise to the formation of chains consisting of alternating anions and cations parallel to [100].