1,5-Dianilinopentane-1,3,5-trione: a crystal structure containing two polymorphic domains

Single crystals of the title compound, C₁₇H₁₆N₂O₃, were obtained by gas diffusion. The observed diffraction pattern is compatible with a superposition of reflections from two monoclinic unit cells with the space group C2/c. The two cells share the a and b axes but not the c axis. Both structures contain layers parallel to (001), with molecules connected by intermolecular N—H...O=C hydrogen bonds. The bonding between adjacent layers is weak. Layer displacements result in a crystal structure containing two closely related polymorphic domains. The structure of one polymorph can be derived from the structure of the other if subsequent layers are displaced by (a/4, b/4, 0) for odd-numbered layers and by (a/4, −b/4, 0) for even-numbered layers. Three different crystals were analysed and their observed diffraction patterns were similar, showing all three crystals to contain the polymorphic domain structure.