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-methyl-imidazole 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 mol-ecule is in its cationic form. The nitrate anion in this structure lies on a twofold rotation axis. The neutral 2-methyl-imidazole mol-ecule and the 2-methyl-1H-imidazol-3-ium cation inter-act 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 inter-act through bifurcated N-H⋯(O,O) hydrogen bonds, giving rise to the formation of chains consisting of alternating anions and cations parallel to [100].

Keywords: 2-methyl-1H-imidazol-3-ium cations; bifurcated hydrogen bonds; chain structure; crystal structure.

Figure 1

The mol­ecular components of salt (I), showing the atom labelling and displacement ellipsoids drawn at the 50% probability level. H atoms are drawn as spheres of arbitrary radius and hydrogen bonds are shown as dashed lines. [Symmetry codes: (i) 1 − x, y,  − z, (ii): 1 − x, y,  − z.]

Figure 2

The mol­ecular components of salt (II), showing the atom labelling and displacement ellipsoids drawn at the 50% probability level. H atoms are drawn as spheres of arbitrary radius and hydrogen bonds are shown as dashed lines.

Figure 3

Partial view of the packing in the crystal structure of (I), showing a chain of hydrogen-bonded mol­ecules. Only one of the statistically disordered H-atom positions between the imidazole rings is shown.

Figure 4

Partial view of the packing in the crystal structure of (II), showing a chain made up of hydrogen-bonded nitrate anions and 2-methyl-1H-imidazol-3-ium cations.