Structural Diversity in 1,3-Bis(m-cyanophenyl)urea

Hydrogen bonding between 1,3-bis ureas is a commonly used motif in the assembly of supramolecular structures such as gels, capsules and crystals. The title compound, 1,3-bis(m-cyanophenyOurea (mCyPU), has previously been shown to crystallize in both an anhydrous and monohydrate phase (alpha and H-I). An expanded search for polymorphs and cocrystals of mCyPU revealed a much greater diversity of solid forms including three additional polymorphs (beta, delta, epsilon), a second hydrate (H-II) and two cocrystal phases with dimethyl sulfoxide and triphenylphosphine oxide. Analysis of the single crystal structures obtained in this study shows that the typical 1-dimensional H-bonding between 1,3-bis urea groups is disrupted by the presence of other H-bond acceptors including cyano, water, sulfoxide and phosphine oxide functionalities. Re-examination of alpha-mCyPU additionally showed both blade and plate-like morphologies could be obtained from different growth solvents, with crystals of the latter morphology exhibiting a grain boundary migration prior to melting.