1-Benzyl-3-methylimidazolium chloride 0.25-hydrate

The asymmetric unit of the title compound, C11H13N2 +·Cl−, contains two independent ion pairs and and half a solvent water molecule (m site symmetry for the O atom). The imidazole ring is oriented at dihedral angles of 66.61 (3) and 89.17 (3)° with respect to the aromatic ring in the two cations. In the crystal, O—H⋯(O,Cl) hydrogen bonds and π–π stacking interactions between the imidazole ring of one molecule and the aromatic ring of another [perpendicular distance = 3.4 (4) Å] link the molecules.


Comment
Ionic liquids (ILs) are a class of compounds composed of organic cations and organic or inorganic anions and have attracted significant attention due to their beneficial properties and their low impact on environment. Many investigations have been dedicated to their use as new media for synthetic chemistry (Fukaya et al., 2006), catalysts for organic synthesis (Ranu et al., 2005;Chen et al., 2005), extractants for separation science (Blanchard et al., 2001) and electrolytes for electrochemistry (Zhang et al., 2006) as well as other areas due to their peculiar physical properties such as a wide liquid range, non-volatility, chemical stability and large windows of electrochemistry. Because it is technically difficult for ionic liquid to grow single crystal and to select suitable sample for single crystal x-ray diffraction at low temperature, so far a few crystal structures have been determined by x-ray diffraction (Katayanagi et al., 2004). We have synthesized a numer of ionic liquids. The title compound is one of the products, and we report herein its crystal structure.
In the molecule of the title compound ( Fig. 1) the bond lengths (Allen et al., 1987) and angles are within normal ranges.
The imidazole ring is oriented with respect to the aromatic ring at a dihedral angle of 89.17 (3)° and 66.61 (3)°, respectively.
The hydrogen bond are formed between one Cl and H 2 O (Table 1). In the crystal structure, π-π packing between the imidazole ring of one molecule and the aromatic ring of the other [perpendicular distance = 3.4 (4)Å] link the molecules. The packing diagram of the O-H···Cl bonds is shown in Fig. 2.

Experimental
For the preparation of the title compound, N-methylimidazole (8.2 g, 0.1 mol) was dissolved in dry acetonitrile (30 ml).

Refinement
H atoms of water were located in a different Fourier map and the atomic coordinates allowed to refine freely. Other H atoms were positioned geometrically and refined as riding (C-H = 0.93-0.96Å) and allowed to ride on their parent atoms, with U iso (H) =1.2U eq (parent) or 1.5U eq (parent).
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.