2-(Naphthalen-1-yl)-1-phenyl-1H-benzimidazole benzene hemisolvate

In the title compound, C23H16N2·0.5C6H6, the benzimidazole unit [maximum deviation = 0.0258 (6) Å] and the naphthalene ring system [maximum deviation = 0.0254 (6) Å] are both essentially planar and make a dihedral angle of 61.955 (17)°. The imidazole ring makes dihedral angle of 61.73 (4)° with the phenyl ring. An intramolecular C—H⋯N hydrogen bond generates an S(6) ring motif. In the crystal, seven weak C—H⋯π interactions involving the fused ring system, the benzene solvent molecule, the imidazole phenyl rings are observed, leading to a three-dimensional architecture.

In the title compound, C 23 H 16 N 2 Á0.5C 6 H 6 , the benzimidazole unit [maximum deviation = 0.0258 (6) Å ] and the naphthalene ring system [maximum deviation = 0.0254 (6) Å ] are both essentially planar and make a dihedral angle of 61.955 (17) . The imidazole ring makes dihedral angle of 61.73 (4) with the phenyl ring. An intramolecular C-HÁ Á ÁN hydrogen bond generates an S(6) ring motif. In the crystal, seven weak C-HÁ Á Á interactions involving the fused ring system, the benzene solvent molecule, the imidazole phenyl rings are observed, leading to a three-dimensional architecture.

Comment
Benzimidazole based chromophores have received increasing attention due to their distinctive linear, non-linear optical properties and also due to their excellent thermal stability in guest-host systems (Cross et al., 1995). They are a component of vitamin B 12 (Brown, 2005) and are related to the DNA base purine and the stimulant caffeine. Substituted benzimidazole derivatives have found commercial applications in veterinarian medicine as anthelmintic agents and in diverse human therapeutic areas as an antiulcer and antihistaminic (Spasov et al., 1999). Therefore, the preparation of benzimidazoles has gained considerable attention in recent years. Jayamoorthy et al., (2012Jayamoorthy et al., ( , 2013 and Rosepriya et al., (2011) have reported closely related structures of benzimidazole derivatives. We are interested to use 2-(naphthalen-1yl)-1-phenyl-1H-benzimidazole as ligand to study its photophysical properties.

Experimental
To the pure N-phenyl-o-phenylenediamine (17 mmol, 3.128 g) in ethanol (10 ml), napthaldehyde (17 mmol, 1.9 ml) and ammonium acetate (3 g) was added about 1 h by maintaining the temperature at 353 K. The reaction mixture was refluxed for 48 hrs and the completion of reaction was monitored by TLC, finally the reaction extracted by dichloromethane. The solid separated was purified by column chromatography using benzene as the eluent. Yield: 2.65 g (50%).
The compound was dissolved in benzene and ethyl acetate (9:1) mixture and allowed to slow evaporation for two days, to obtain crystals suitable for X-ray diffraction studies.

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as small spheres of arbitrary radius. The dashed line indicates the intramolecular C-H···N hydrogen bond.