2-(3,4-Difluorophenyl)-1H-benzimidazole

In the title molecule, C13H8F2N2, the dihedral angle between the benzimidazole ring system and the difluoro-substituted benzene ring is 30.0 (1)°. In the crystal, molecules are linked by N—H⋯N hydrogen bonds, forming chains along [010]. In addition, weak C—H⋯F hydrogen bonds connect chains into a two-dimensional network parallel to (001). A weak C—H⋯π interaction is observed between an H atom of the benzimidazole ring sytem and the π system of the difluoro-substituted benzene ring.

In the title molecule, C 13 H 8 F 2 N 2 , the dihedral angle between the benzimidazole ring system and the difluoro-substituted benzene ring is 30.0 (1) . In the crystal, molecules are linked by N-HÁ Á ÁN hydrogen bonds, forming chains along [010]. In addition, weak C-HÁ Á ÁF hydrogen bonds connect chains into a two-dimensional network parallel to (001). A weak C-HÁ Á Á interaction is observed between an H atom of the benzimidazole ring sytem and the system of the difluorosubstituted benzene ring.
NSB is thankful to the University Grants Commission (UGC), India, for financial assistance. Benzimidazole is a bicyclic heterocycle system consisting of two nitrogen atoms and fused phenyl ring. It shows wide variety of pharmacological activities such as antihypertensive (Kubo et al., 1993), anti-HIV (Chimirri et al., 1991), antiulcer (Ishihara et al., 1994). The bond lengths and bond angles of the benzimidazole moiety in the title compound are in good agreement with those observed in other benzimidazole derivatives (Jayamoorthy et al., 2012;Yoon et al., 2012).
The molecular structure of the title compound is shown in Fig. 1. The dihedral angle between the benzimidazole ring system and difluoro-substituted benzene ring is 30.0 (1)°. This value is slightly larger than for the benzene ring with a trifluoromethoxy substituent at the para position (Fathima et al., 2013), and slightly smaller for a ring with a fluorine atom at the para position (Rashid et al., 2007). In the crystal, molecules are linked by intermolecular N1-H1···N2 i and C9-H9···F2 ii hydrogen bonds (see Table 1 for symmetry codes). The former interaction forms extended chains parallel to the b-axis and the latter results in one-dimensional chains along the a-axis (Fig. 2). Overall a two-dimensional network parallel to (001) is formed. In addition, a weak C-H···π interaction of the type C3-H3A···Cg (Cg being the centroid of the ring C9-C13 ring) is observed (Table 1).

Experimental
The title compound was synthesized by refluxing 3,4-difluorobenzaldehyde (20 mmol,0.28 g) and o-phenyldiamine (20 mmol,0.22 g) in benzene (3.0 ml) for 6hrs on a water bath. The reaction mixture was cooled. The solid separated, was filtered and dried (Yield; 0.34 g (75%) and M.P. 533 K). Yellow crystals of the title compound were obtained by slow evaporation of a solution of the title compound in ethyl acetate.

Refinement
The H atoms were placed in calculated positions and refined in a riding-model approximation with C-H = 0.93 Å, N-H = 0.86 Å and with U iso (H) = 1.2U eq (N/C).

Figure 2
Part of the crystal structure showing intermolecular hydrogen bonds with dashed lines. H-atoms not involved in hydrogen bonds have been excluded. The atoms N2 and F2 are related by the symmetry operators (-x+3/2, y+1/2, z) and (x+1/2, -y+3/2, -z+1) respectively. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.47 e Å −3 Δρ min = −0.31 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.