1,3-Bis[(6-methyl-2-pyridyl)methyl]imidazolium bromide

The title compound, C17H19N4 +·Br−, is built up from 1,3-bis[(6-methyl-2-pyridinyl)methyl]imidazolium cations and bromide anions. Each of two 6-methyl-2-pyridyl rings is rotated out of the imidazole plane, making dihedral angles of 79.90 (9) and 86.40 (9)°. The packing is consolidated by aromatic π–π interactions between the pyridine rings of neighbouring molecules [centroid–centroid distance = 3.554 (2) Å] and by weak C—H⋯N and C—H⋯Br hydrogen bonds.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: LX2088).
The asymmetric unit of the title compound consists the C 17 H 9 N 4 cation and Br anion. Each of two 6-methylpyridine rings is rotated out of the imidazole plane, with dihedral angle of N1/C2-C6 of 79.90 (9)° and N4/C12-C16 of 86.40 (9)°, respectively. The crystal packing (Fig. 2) is stabilized by intermolecular aromatic π-π interactions between the pyridine rings of neighbouring molecules. The Cg-Cg iii distance of 3.554 (2) Å (Cg is the centroid of the N1/C2-C6 pyridine ring; symmetry code as in Fig. 2). The molecular packing is further stabilized by C-H···N interactions between the hydrogen of 7-methylene group and the N atom of pyridine ring of the neighbouring molecule, with a C7-H7A···N4 i separation of 2.34 (1) Å (Table 1 and Fig. 2; symmetry code as in Fig. 2). Additionally, five different intermolecular C-H···Br hydrogen bonds in the structure are observed (Table 1 & Fig. 2).
Synthesis of [H(MepyCH 2 ) 2 -Im]Br (1): A mixture of (1a), H(MepyCH 2 )Im, (0.52 g, 3.0 mmol) and 2-bromomethyl-6methylpyridine (0.56 g, 3.0 mmol) in toluene (50 mL) was refluxed at 383 K for 14 h. After cooling, the solvents were All H atoms were geometrically positioned and refined using a riding model, with C-H = 0.95 Å for the aryl, 0.99 Å for the methylene, and 0.00 Å for the methyl H atoms, respectively, and with Uiso(H) = 1.2Ueq(C) for the aryl and methylene H atoms, and 1.5Ueq(C) for the methyl H atoms. Fig. 1. The molecular structure of the title compound, showing displacement ellipsoids drawn at the 50% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.