Structural Diversity in 1,3-Bis(<i>m</i>-cyanophenyl)urea

Abstract

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 -cyanophenyl)urea ( mCyPU ), has previously been shown to crystallize in both an anhydrous and monohydrate phase (α and H–I). An expanded search for polymorphs and cocrystals of mCyPU revealed a much greater diversity of solid forms including three additional polymorphs (β, δ, ε), 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 α-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.