Polymorphic structures of 3-phenyl-1H-1,3-benzo-diazol-2(3H)-one

The two polymorphic structures of 3-phenyl-1 H -1,3-benzo­diazol-2(3 H )-one ( I and II ) exhibit identical bond distances and angles except for the C—N—C—C torsion angle between the benzimidazolone backbone and the phenyl substituent, which has an effect on the crystal packing and supra­molecular features. The structure of I contains a stronger C=O⋯H—N hydrogen-bonding inter­action and a weaker π–π inter­action between adjacent bezimidazolone moieties in comparison to II . The polymorphic structures ( I and II ) of 3-phenyl-1 H -1,3-benzo­diazol-2(3 H )-one, C 13 H 10 N 2 O, acquired from pentane diffusion into the solution in THF, are reported. The structures show negligible differences in bond distances and angles, but the C—N—C—C torsion angles between the backbone and the phenyl substituent, 123.02 (15)° for I and 137.18 (11)° for II , are different. Compound I features a stronger C=O⋯H—N hydrogen bond than that in II , while the structure of II exhibits a stronger π–π inter­action than in I , as confirmed by the shorter inter­centroid distance [3.3257 (8) Å in II in comparison to 3.6862 (7) Å in I ]. Overall, the supra­molecular inter­actions of I and II are distinct, presumably originating from the variation in the dihedral angle.