2-Hydroxymethyl-1,3-dimethyl-1H-imidazol-3-ium triiodide

The crystal packing of the title salt, C6H11N2O+·I3 −, can be described as consisting of alternating layers of cations and anions parallel to the (100) plane along the a-axis direction. The components are linked by O—H⋯I, C—H⋯I and C—H⋯O interactions, generating a three-dimensional network. The O atom deviates from the imidazol ring by 0.896 (2) Å.

The crystal packing of the title salt, C 6 H 11 N 2 O + ÁI 3 À , can be described as consisting of alternating layers of cations and anions parallel to the (100) plane along the a-axis direction. The components are linked by O-HÁ Á ÁI, C-HÁ Á ÁI and C-HÁ Á ÁO interactions, generating a three-dimensional network. The O atom deviates from the imidazol ring by 0.896 (2) Å .
We are grateful to all personal of the research squad "Synthè se de molé cules à objectif thé rapeutique" of PHYSYNOR Laboratory, Université Constantine1, Algeria, for their assistance. Thanks are due to MESRS (Ministé re de l'Enseignement Supé rieur et de la Recherche Scientifique -Algé rie) for financial support. Sheldrick, G. M. (2008 (Pandey et al., 2009;Nasser, 2000). Imidazole is a nitrogen containing heterocyclic ring which possesses biological and pharmaceutical importance (Ozkay, et al., 2010). It forms the main structure of some well known components of human organisms, i.e. the amino acid histidine, Vit-B12, a component of DNA base structure and purines, histamine and biotin (Ucucu, et al., 2001). In other hand, imidazolium salts are known for the wide range of their biological activity. A large variety of these salts have been used as anti-inflammatory, antibacterial, antifungal and thromboxane synthetase inhibitior (Dominianni et al., 1989). In continuation of our studies on imidazole derivatives (Bahnous et al., 2012;Zama et al., 2013 andChelghoum et al., 2011). We report herein the synthesis and crystal structure of a new imidazolium salt, I, bearing two methyl groups at C-1 and C-3 positions, a hydroxymethyl at C-2 and a triiodide anion that balance the charge.
The molecular geometry and the atom-numbering scheme of (I) are shown in Fig. 1. The asymmetric unit of title molecule, C 6 H 11 N 2 O, I 3 , contains a 1,3-dimethyl-2-hydroxymethylidazolium cation and triiodide anion. The crystal packing can be described as alternating layers parallel to the (100) plane along the a axis, where triiodide anion is located in these layers (Fig. 2) and they are linked together by O-H···I, C-H···I and C-H···O intermolecular hydrogen bonds As shown in the Figure 2, the imidazol rings of the symmetry related layers are intercalated, however the centroid to centroid distance between the imidazol rings are too long (5.3400 (19) and 5.6641 (19) Å) for considering π-π interactions. These interaction bonds link the molecules within the layers and also link the layers together, reinforcing the cohesion of the ionic structure. Hydrogen-bonding parameters are listed in table 1.

Experimental
The treatment of 1,3-dimethyl-2-hydroxymethylimidazolium iodide (Chelghoum et al., 2011) with diluted sulfuric acid solution, during ten days in opened flask for slow evaporation, gave the title compound as a brown crystals. The crystals are filtered off and washed with water. Suitable crystal of compound (I) was selected and X-ray crystallographic analysis confirmed the structural assignment (Fig. 1).

Refinement
Approximate positions for all the H atoms were first obtained from the difference electron density map. However, the H atoms were situated into idealized positions and the H-atoms have been refined within the riding atom approximation.

Figure 1
The molecular geometry of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radius.

Figure 2
Alternating layers of (I) viewed down the c axis showing hydrgen bond as dashed line.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.