5,6-Dimethyl-2-(5-methylthiophen-2-yl)-1-[(5-methylthiophen-2-yl)methyl]-1H-benzimidazole

The title molecule, C20H20N2S2, is T-shaped and consists of a nearly flat 5,6-dimethyl-2-(5-methylthiophen-2-yl)benzimidazole system approximately perpendicular to the 5-methylthiophen-2-ylmethyl substituent. The 5,6-dimethyl-2-(5-methylthiophen-2-yl)benzimidazole system is rotationally disordered about the two imidazole N atoms as approximated by a twofold rotation axis with a refined major/minor occupancy ratio of 0.884 (2):0.116 (2). The benzimidazole ring system is essentially planar, the largest deviations being 0.026 (2) and 0.044 (18) Å in the major and minor components, respectively. The interplanar angles between the benzimidazole unit and the 5-methylthiophen-2-yl substituent are 10.8 (3) and 8(3)° in the major and minor components, respectively, and the corresponding angles with the 5-methylthiophen-2-ylmethyl substituent are 88.12 (8) and 89.5 (4)°. In the crystal, molecules are oriented with their 2-(5-methylthiophen-2-yl)benzimidazole mean planes approximately parallel to (11) and appear to be held together by π–π [2-thiophene⋯imidazole centroid–centroid distance = 4.1383 (7) Å] and C—H⋯π contacts. A weak C—H⋯N hydrogen bond generates infinite chains parallel to [100].


Experimental
The title compound was prepared by stirring 4,5-dimethyl-1,2-diaminobenzene (0. Crystals suitable for X-ray analysis were obtained by vapor diffusion of hexane into a concentrated chloroform solution.

Refinement
Crystal data, data collection and structure refinement details are summarized in the crystallographic data table. The resolution of the data was limited to 0.84 Å (θ max = 25.1°) because the data quality dropped of markedly at higher resolution. For the shell from 0.85 to 0.84 Å, the mean I/σ was 3.47.
During the initial stages of refinement, it became obvious that the molecule exhibited twofold rotational disorder. The disorder was successfully modeled using the metrics of the major component to define the minor component. Similarity restraints were used for the bond distances using SAME and anisotropic displacement parameters of the minor component atoms were constrained to those of the major component using EADP.  Packing diagram showing the hydrogen bonding network forming infinite chains parallel to [100]. All hydrogen atoms except H12A have been omitted for clarity. C12-H12A···N2 hydrogen bonds are represented by dashed lines. Only the major contributor to the disorder model is shown.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (