2-(4-Fluorophenyl)-1-phenyl-1H-benzimidazole

In the title molecule, C19H13FN2, the benzimidazole unit is close to planar [maximum deviation = 0.0342 (9) Å] and forms dihedral angles of 58.94 (3) and 51.43 (3)° with the phenyl and fluorobenzene rings, respectively; the dihedral angle between the phenyl and fluorobenzene rings is 60.17 (6)°. In the crystal, three C—H⋯F hydrogen bonds and two weak C—H⋯π interactions involving the fused benzene ring lead to a three-dimensional architecture.

In the title molecule, C 19 H 13 FN 2 , the benzimidazole unit is close to planar [maximum deviation = 0.0342 (9) Å ] and forms dihedral angles of 58.94 (3) and 51.43 (3) with the phenyl and fluorobenzene rings, respectively; the dihedral angle between the phenyl and fluorobenzene rings is 60.17 (6) . In the crystal, three C-HÁ Á ÁF hydrogen bonds and two weak C-HÁ Á Á interactions involving the fused benzene ring lead to a threedimensional architecture.
can be easily tailored to accommodate functional groups, which allows the covalent incorporation of the NLO chromophores into polyamides leading to NLO side chain polymers (Bu et al., 1996). Most π-conjugated systems play a major role in determining second-order NLO response (Dirk et al., 1990). Since our group is doing research in organic light emitting devices (OLEDs), we are interested in using the title compound as a ligand in the preparation of Ir(III) complexes and in studying the photophysical properties of these complexes. Rosepriya et al. (2011) have reported a related crystal structure, namely 1-(4-Methylbenzyl)-2-(4-methylphenyl)-1H-benzimidazole.

Experimental
To N-phenyl-o-phenylenediamine (3.128 g, 17 mmol) in ethanol (10 ml) was added 4-fluorobenzaldehyde (1.9 ml, 17 mmol) and ammonium acetate (3 g) over about 1 h while maintaining the temperature at 353 K. The reaction mixture was refluxed until the completion of reaction, as monitored by TLC. The reaction mixture was extracted with dichloromethane. The solid that separated out was purified by column chromatography using petroleum ether: ethyl acetate as the eluent. Yield: 2.47 g (50%). The title compound was dissolved in acetonitrile and allowed to slowly evaporate for two days to obtain crystals suitable for X-ray diffraction studies.

Refinement
The H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C).

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 > 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.