2-[4-(Trifluoromethyl)phenyl]-1H-benzimidazole

In the title compound, C14H9F3N2, the mean planes of the benzimidazole ring system and the trifluoromethyl-substituted benzene ring form a dihedral angle of 30.1 (1)°. In the crystal, molecules are linked by N—H⋯N hydrogen bonds into chains along [010]. Weak C—H⋯F hydrogen bonds and a weak C—H⋯π interaction connect the chains into a two-dimensional network parallel to (001).

Supporting information for this paper is available from the IUCr electronic archives (Reference: LH5706). Benzimidazole and its derivatives are regarded as a promising class of bio-active heterocyclic compounds that exhibit a range of biological activities such as antibacterial (Ozden et al., 2004), anticancer (Easman et al.,2001, anti-HIV and anti-inflammatory (Ansari & Lal 2009;Thakurdesai et al., 2007). In addition, compounds which contain fluorine have special bioactivity (Ulrich, 2004). The bond lengths and bond angles of the benzimidazole moiety in the title compound are in good agreement with those observed in related structures (Jian et al., 2006;Rashid, et al., 2007;Rosepriya et al., 2011). The title compound is closely related to our previously reported compounds (Fathima et al., 2013;Krishnamurthy et al., 2013). The molecular structure of the title compound is shown in Fig. 1. The dihedral angle between the benzimidazole ring system and the trifluoro-substituted benzene ring is 30.1 (1)°. In the crystal structure, molecules are linked by N-H···N hydrogen bonds to form chains parallel to [010]. In addition, weak C-H···F hydrogen bonds and a weak C-H···π interaction connect chains into a two-dimensional network parallel to (001) (Fig. 2). The weak C-H···π interaction involves the centroid of the N1/C5/C6/N2/C7 ring (Table 1). In addition, the crystal packing involves the presence of short F···F contacts of 2.915 (3) Å.

Experimental
A mixture of 4-(trifluoromethyl)bezaldehyde (20 mmol, 0.35 g) and o-phenyldiamine (20 mmol, 0.22 g) in benzene (5.0 ml) was refluxed for 6 hrs on a water bath. The reaction mixture was cooled. The solid separated, was filtered and dried (yield: 0.38 g, 78% and m.p. 538 K). The title compound was dissolved in ethyl acetate and kept aside for slow evaporation to obtain pale yellow crystals suitable for X-ray diffraction studies.

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).  The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level. H atoms are presented as small spheres of arbitrary radius.

Figure 2
Part of the crystal structure showing hydrogen bonds with dotted lines. H-atoms not involved in hydrogen bonding have been excluded. The atoms labeled C13, N1 and C12 are related by the symmetry operators: -0.5+x, 1.5-y, -z; 1.5-x, 0.5+y, z and 0.5-x, -0.5+y, z, respectively.

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.