1-(4-tert-Butylbenzyl)-2-(4-tert-butylphenyl)-1H-benzimidazole

In the molecule of the title compound, C28H32N2, the benzimidazole ring system is almost planar [maximum deviation = 0.0221 (15) Å] and forms dihedral angles of 85.86 (4) and 32.09 (6)° with the benzene rings. In the crystal structure, molecules are linked into chains running parallel to the a axis by intermolecular C—H⋯N hydrogen bonds. The methyl groups of a tert-butyl group are rotationally disordered over two positions with refined site-occupancy factors of 0.636 (4) and 0.364 (4).

In the molecule of the title compound, C 28 H 32 N 2 , the benzimidazole ring system is almost planar [maximum deviation = 0.0221 (15) Å ] and forms dihedral angles of 85.86 (4) and 32.09 (6) with the benzene rings. In the crystal structure, molecules are linked into chains running parallel to the a axis by intermolecular C-HÁ Á ÁN hydrogen bonds. The methyl groups of a tert-butyl group are rotationally disordered over two positions with refined site-occupancy factors of 0.636 (4) and 0.364 (4).

Comment
Imidazole and benzimidazole derivatives are important heteroaromatic compounds which have attracted great attention due to their biological and pharmaceutical activities (Matsuno et al., 2000;Garuti et al., 1999). These compounds have also played an important role in the development of coordination chemistry. In this paper, we report the crystal structure of the title compound.
The molecular structure of the title compound is shown in Fig. 1. Bond lengths (Allen et al., 1987) and angles are within normal ranges. The benzimidazole ring system is substantially planar, with a maximum displacement of 0.0221 (15) Å for atom C1. The dihedral angle it forms with the C8-C13 and C19-C24 benzene rings are 32.09 (6) and 85.86 (4) Å, respectively. The benzene rings are oriented perpendicularly to each other, forming a dihedral angle of 89.58 (5) °. In the crystal packing, the molecule are linked into chains running parallel to the a axis by intermolecular C-H···N hydrogen bonds (Table 1). The methyl groups of a tert-butyl group exhibits rotational disorder over two orientations with site occupation factors of 0.636 (4) and 0.364 (4) for the major and minor components of disorder, respectively.

Experimental
To a solution of o-phenylenediamine (0.432 g, 4 mmol) in ethanol(20 ml), 4-tert-butylbenzaldehyde (1.297 g, 8 mmol) was added. The mixture was heated to reflux with stirring for four hour, then cooled to room temperature. The resultant solution was filtered and allowed to evaporate slowly at room temperature. Colourless single crystals of the title compound suitable for X-ray diffraction study were obtained after several weeks.

Refinement
The C15, C16 and C17 methyl carbon atoms of a tert-butyl group are rotationally disordered over two position with refined site occupancy factors of 0.636 (4) and 0.364 (4). All H atoms were located geometrically and treated as riding atoms, with C-H = 0.93-0.97 Å, and with U iso (H) = 1.2 U eq (C) or 1.5 U eq (C) for methyl H atoms. Fig. 1. The molecular structure of the title compound, showing the atomic numbering scheme. The displacement ellipsoids are drawn at the 30% probability level.