1-Phenyl-2-p-tolyl-1H-benzimidazole

In the title compound, C20H16N2, the benzimidazole ring system forms dihedral angles of 28.50 (7) and 72.44 (7)° with the tolyl and phenyl rings, respectively. In the crystal, molecules are linked into chains along the a-axis direction by weak C—H⋯N interactions. The crystal structure also features C—H⋯π interactions.


Comment
Benzimidazoles play an important role in the development of coordination chemistry. Benzimidazole derivatives have attracted considerable attention because of their biological and pharmaceutical activities (Garuti et al., 1999;Matsuno et al., 2000).
Because of their wide optical absorption, bright luminescence and bipolar transport characteristics, fused imidazole derivatives, such as benzoimidazoles and phenanthroimidazoles (Fang et al., 2007;Ge et al., 2008;Lai et al., 2008), have been used in the fabrication of light-emitting devices, employing them as electron-transporting layer and as sensitizers in dye-sensitized solar cells (Shin et al., 2007). Benzimidazole derivatives possess antioxidant, antimicrobial and antifungal activities. In view of their importance, the structure determination of the title compound was carried out and the results are presented herein.
The asymmetric unit contains one molecuale of the title compound (I). The bond lengths and bond angles are within normal ranges (Allen et al., 1987). X-ray analysis confirms the molecular structure and atom connectivity of the compound as illustrated in Fig. 1.
The planar benzimidazole ring system N1/C7/N2/C6/C1-C5 is oriented with respect to the adjacent tolyl and phenyl rings, C8-C14 and C15-C20, with dihedral angles of 28.50 (7)° and 72.44 (7)° respectively. In the crystal structure, the molecules are linked into chains along the a axis by intermolecular C-H···N hydrogen bonds. The crystal structure is further stabilized by the weak intermolecular C-H···π(Cg1) interaction (Table 1), where Cg1 is the centre of gravity of the C15-C20 phenyl ring.
The packing view of the title compound is shown in Fig 2. Experimental N-phenyl-o-phenylenediamine (17 mmol, 3.128 g) was dissolved in ethanol (10 ml), then 4-methyl benzaldehyde (17 mmol, 2.1 ml) and ammonium acetate (3 g) were added, maintaining the temperature at 80°C for about an hour. The reaction mixture was refluxed for 48 h and the completion of the reaction was monitored by TLC. After completion of the reaction, the mixture was extracted with dichloromethane. The solid separated was purified by column chromatography using petroleum ether as the eluent. Yield: 2.82 g (50%). Single crystals were grown in ethanol as a solvent at room temperature.

Refinement
The hydrogen atoms were placed in calculated positions with C-H= 0.93 Å to 0.96 Å, and refined in the riding model with fixed isotropic displacement parameters: U iso (H) = 1.5U eq (C) for methyl group and U iso (H) = 1.

Figure 1
The molecular structure and labelling scheme for (I) with displacement ellipsoids for non-H atoms drawn at the 30% probability level.  Packing diagram of (I). Dashed lines indicate intermolecular hydrogen bonding interactions. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.12 e Å −3 Δρ min = −0.11 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0073 (6) Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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 > σ(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.