Structural and dynamic properties of urea and thiourea inclusion compounds

There is currently considerable interest in the chemistry and physics of solid inclusion compounds as a consequence of the wide range of important physico-chemical properties associated with them. In part, scientific interest in these materials is motivated by the desire to compare the structural, dynamic, and chemical properties of organic ''guest'' molecules embedded within different crystalline environments, and to investigate how the properties of the guest molecule may be influenced by the structural characteristics of its environment. This paper is focused upon urea and thiourea inclusion compounds containing a variety of different types of organic guest molecule. Aspects of the structural and dynamic properties of these inclusion compounds have been probed using solid-state NMR spectroscopy, X-ray diffraction, EXAFS spectroscopy, incoherent quasielastic neutron scattering, Raman spectroscopy, computer simulation and mathematical modelling. On the basis of the results from these investigations, the current level of understanding of the structural and dynamic properties of these materials is assessed.