2-(1H-Benzoimidazol-2-yl)-6-ethoxyphenol

The title Schiff base compound, C15H14N2O2, consists of two crystallographically independent molecules, A and B. Molecule A is almost planar, whereas molecule B is slightly twisted, the dihedral angles between the benzimidazole group and the benzene rings being 2.65 (12) and 13.17 (15)°, respectively. The methyl group of molecule B is disordered over two positions, with a refined site-occupancy ratio of 0.581 (7):0.419 (7). In each molecule, intramolecular O—H⋯N hydrogen bonds generate S(6) ring motifs. In the crystal structure, both types of molecules are linked via intermolecular bifurcated N—H⋯O hydrogen bonds into one-dimensional extended chains along [010] and form R 1 2(5) ring motifs. The crystal structure is further stabilized by intermolecular C—H⋯π and π–π interactions [centroid–centroid distances = 3.4758 (16)–3.596 (2) Å].

The title Schiff base compound, C 15 H 14 N 2 O 2 , consists of two crystallographically independent molecules, A and B. Molecule A is almost planar, whereas molecule B is slightly twisted, the dihedral angles between the benzimidazole group and the benzene rings being 2.65 (12) and 13.17 (15) , respectively. The methyl group of molecule B is disordered over two positions, with a refined site-occupancy ratio of 0.581 (7):0.419 (7). In each molecule, intramolecular O-HÁ Á ÁN hydrogen bonds generate S(6) ring motifs. In the crystal structure, both types of molecules are linked via intermolecular bifurcated N-HÁ Á ÁO hydrogen bonds into one-dimensional extended chains along [010] and form R 1 2 (5) ring motifs. The crystal structure is further stabilized by intermolecular C-HÁ Á Á andinteractions [centroidcentroid distances = 3.4758 (16)-3.596 (2) Å ].

Comment
Benzimidazoles are used widely in biological applications and as pharmaceutical agents (Craigo et al., 1999;Gudmundsson et al., 2000;Trivedi et al., 2006). They are also used as topoisomerase I inhibitors (Kim et al., 1996) and for antitumor activity (Ramla et al., 2006). Due to these important applications, many synthetic routes towards benzimidazoles have been developed. They can, for example, be synthesized by the reaction of phenolic aldehydes with o-phenylenediamine (Latif et al.,, 1983). Based on this route the title compound was synthesized and its crystal structure is reported here.
The asymmetric unit of the title compound, Fig. 1, consists of two crystallographically independent molecules, A and B with a slightly different conformations due to a disordered group. Intramolecular O-H···N hydrogen bonds generate S(6) ring motifs (Bernstein et al., 1995). The two molecules A and B are linked together by a bifurcated hydrogen bond involving the two oxygen atoms of the hydroxy and ethoxy groups with a R 1 2 (5) ring motif. The molecule A is almost planar wheares the molecule B is slightly twisted with the dihedral angles between the benzimidazole and the phenyl rings being 2.65 (12) and 13.17 (15) °, respectively. The methyl group of molecule B is disordered over two positions with a refined site-occupancy ratio of 0.581 (7):0.419 (7). The crystal structure is further stabilized by intermolecular C-H···π [Cg1, Cg2 and Cg3 are the centroids of the C8B-C13B, C1B-C6B and N1A/C1A/C6A/N2A/C7A rings] (Table 1)

Experimental
An ethanolic solution (50 ml) of 3-ethoxy-salicylaldehyde (2 mmol, 332 mg) was added to 1,2-phenylenediamine (1 mmol, 217 mg). The mixture was refluxed for 2 h, and cooled to room temperature. The resulting colourless powder was filtered, washed with cooled ethanol and dried in vacuo. Single crystals suitable for X-ray diffraction were obtained from an methanol solution at room temperature.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems 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 )