Polymorphism in a symmetrical dipeptidyl urea with Z' > 1

Two polymorphic forms of a symmetrical Aib containing urea derivative, DIPUR(α) and DIPUR, have been structurally characterized using synchrotron/X-ray diffraction data with a detailed analysis of Hirshfeld surfaces and fingerprint plots facilitating a comparison of the type and nature of intermolecular interactions in the supramolecular architectures. Structural study of DIPUR(α) crystallizing in a Sohnke space group P21 reveals four crystallographically independent molecules (A, B, C, and D) in the asymmetric unit with the pairs of molecules A, B and C, D interlinked via N-H•••O hydrogen bonds forming antiparallel one-dimensional chains having a C22(8)R21(6)R 21(6) sequence. The combination of intermolecular N-H•••O and C-H•••O hydrogen bonds generates a three-dimensional framework in DIPUR(α). In the polymorph DIPUR(β) with space group P212121 and Z' = 2, the N-H•••O-bonded R22(11) rings propagate along the [001] direction through C22(8) chains to form a one-dimensional molecular assembly. The Aib residues in DIPUR(α) and DIPUR(β) induce constraints on the molecular interactions and facilitate a network of hydrogen bonds in both polymorphs. © 2010 American Chemical Society.