2-Methyl-6-(6-methyl-1H-benzimidazol-2-yl)phenol–2-methyl-6-(5-methyl-1H-benzimidazol-2-yl)phenol (3/1)

The title compound, 0.75C15H14N2O·0.25C15H14N2O, is a co-crystal of 2-methyl-6-(6-methyl-1H-benzimidazol-2-yl)phenol as the major component and 2-methyl-6-(5-methyl-1H-benzimidazol-2-yl)phenol as the minor component. The refined site-occupancy ratio is 0.746 (4)/0.254 (4). The conformations of both components are identical except for that of the methyl substituent on the benzene ring of the benzimidazole unit which is positionally disordered over two positions. The molecule is essentially planar, the dihedral angle between the benzimidazole plane and the benzene ring being 3.49 (4)°. An intramolecular O—H⋯N hydrogen bond generates an S(6) ring motif. In the crystal packing, molecules are linked through N—H⋯O hydrogen bonds into chains along [201]. These chains are stacked approximately along the a-axis direction. The crystal packing is further stabilized by weak N—H⋯O and O⋯H⋯N hydrogen bonds, together with weak intermolecular C—H⋯π interactions. A π–π interaction with a centroid–centroid distance of 3.6241 (6) Å is also observed between the substituted phenyl ring and that of the benzimidazole system.

The title compound, 0.75C 15 H 14 N 2 OÁ0.25C 15 H 14 N 2 O, is a cocrystal of 2-methyl-6-(6-methyl-1H-benzimidazol-2-yl)phenol as the major component and 2-methyl-6-(5-methyl-1H-benzimidazol-2-yl)phenol as the minor component. The refined site-occupancy ratio is 0.746 (4)/0.254 (4). The conformations of both components are identical except for that of the methyl substituent on the benzene ring of the benzimidazole unit which is positionally disordered over two positions. The molecule is essentially planar, the dihedral angle between the benzimidazole plane and the benzene ring being 3.49 (4) . An intramolecular O-HÁ Á ÁN hydrogen bond generates an S(6) ring motif. In the crystal packing, molecules are linked through N-HÁ Á ÁO hydrogen bonds into chains along [201]. These chains are stacked approximately along the a-axis direction. The crystal packing is further stabilized by weak N-HÁ Á ÁO and OÁ Á ÁHÁ Á ÁN hydrogen bonds, together with weak intermolecular C-HÁ Á Á interactions. Ainteraction with a centroid-centroid distance of 3.6241 (6) Å is also observed between the substituted phenyl ring and that of the benzimidazole system.

Comment
Benzimidazoles are regarded as a promising class of bioactive heterocyclic compounds that exhibit a variety of bioactivities displaying antidiabetic (Minoura et al., 2004), antimicrobial, antifungal (Guven et al., 2007;Pawar et al., 2005), antiviral (Tomei et al., 2003); anti-inflammatory (Thakurdesai et al., 2007) and anticancer (Demirayak et al., 2002) properties. As part of our research on screening benzimidazoles for their biological activities, we have previously reported the synthesis and crystal structures of some benzimidazoles (Eltayeb et al., 2007;2009a,b). In continuation of this research the title compound (I) was synthesized and its crystal structure is reported here.
Yellow needle-shaped single crystals of the title compound suitable for x-ray structure determination were obtained by slow evaporation of the filtrate at room temperature over several days.

Refinement
Hydroxy and amide H atoms were located in a difference map and refined isotropically. The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.93 Å for aromatic and 0.96 Å for CH 3 supplementary materials sup-2 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups. The highest residual electron density peak is located at 0.70 Å from C8 and the deepest hole is located at 1.17 Å from C7. One methyl group is positionally disordered over two positions with occupancies 0.746 (4) (for the methyl group bound to C10) and 0.254 (4) (for the methyl group bound to C11), respectively. Fig. 1. The molecular structure of the title compound, with 50% probability displacement ellipsoids and the atom-numbering scheme. Open bonds show the minor disorder component 2-Methyl-6-(6-methyl-1H-benzimidazol-2-yl)phenol-2-methyl-6-(5-methyl-1H-benzimidazol-2-yl)phenol (3/1)

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (