Key indicators: single-crystal X-ray study; T = 296 K; mean (C-C) = 0.002 Å; R factor = 0.044; wR factor = 0.122; data-to-parameter ratio = 19.6.In the title compound, C 15 H 14 N 2 O, the fused five-and sixmembered ring system is essentially planar, the maximum deviation from the mean plane being 0.009 (1) Å . The benzimidazol-2(3H)-one residue is nearly perpendicular to the benzyl ring, forming a dihedral angle of 77.41 (6) . In the crystal, inversion dimers are formed by pairs of N-HÁ Á ÁO hydrogen bonds; these dimers are linked by weak C-HÁ Á ÁO interactions into a two-dimensional array in the (102) plane. Related literature Data collectionBruker X8 APEXII diffractometer 16486 measured reflections 3211 independent reflections 2157 reflections with I > 2(I) R int = 0.029