3-Allyl-6-bromo-1H-imidazo[4,5-b]pyridin-2(3H)-one

In the title compound, C15H14N2O4, (I), the mol­ecule lies on a twofold rotation axis which passes through the central C atom of the aliphatic chain, giving one half-mol­ecule per asymmetric unit. The structure is a monoclinic polymorph of the triclinic structure previously reported [Brito, Vallejos, Bolte & López-Rodríguez (2010). Acta Cryst. E66, o792], (II). The most obvious difference between them is the O/C/C/C—O/C/C/C torsion angle [58.2 (7)° in (I) and 173.4 (3)/70.2 (3)° in (II) for GG and TG conformations, respectively]. Another important difference is observed in the dihedral angle between the planes of the aromatic rings [86.49 (7)° for (I) and 76.4 (3)° for (II)]. The crystal structure features a weak π–π inter­action [centroid–centroid distance = 4.1397 (10)Å]; this latter kind of inter­action is not evident in the triclinic polymorph

1-Octyl-1H-benzimidazol-2(3H)-one

In the title compound, C15H22N2O, the octyl group adopts an all-trans conformation. In the crystal, mol­ecules form centrosymmetric dimers with an R 2 2(8) graph-set motif, linked by pairs of N—H⋯O hydrogen bonds. In addition, C—H⋯O contacts are observed

1-Decyl-6-nitro-1H-benzimidazol-2(3H)-on

The title mol­ecule, C17H25N3O3, is built up from fused six- and five-membered rings linked to a –C10H21 chain. The fused-ring system is essentially planar, the largest deviation from the mean plane being 0.009 (2) Å. The chain is roughly perpendic­ular to this plane, making a dihedral angle of 79.5 (2)°. In the crystal, N—H[cdots, three dots, centered]O hydrogen bonds build infinite chains along [010]. There are channels in the structure containing disordered hexane. The contribution of this solvent to the scattering power was suppressed using the SQUEEZE option in PLATON [Spek (2009 [triangle]). Acta Cryst. D65, 148–155]