Two 1-substituted 4-nitroimidazoles

Crystalline 4-nitro-1-phenyl­imidazole, C9H7N3O2, (I), and 4′-­nitro-1-phenyl-4,1′-bii­imidazole, C12H9N5O2, (II), contain C—H⃛O and C—H⃛N hydrogen bonds, connecting the mol­ecules into infinite chains. The aromatic fragments in both compounds are nearly planar. The dihedral angles between the benzene and imidazole rings are 26.78 (5)° in (I) and 29.36 (8)° in (II).