Explorations in the Dynamics of Crystalline Solids and the Evolution of Crystal Formation Processes

This article describes a few selected areas of research within the field of structural chemistry, with emphasis on aspects that have been influenced and inspired by the seminal work of Jack Dunitz. The topics covered include the study of dynamic properties of crystalline materials, focusing on the use of solid-state ²H NMR spectroscopy to unravel details of dynamic hydrogen-bonding arrangements in crystalline alcohols and amino acids, as well as the use of in situ Raman microspectrometry to explore molecular transport processes through porous crystals. A case study involving the determination of both structural properties and dynamic properties of a material (ammonium cyanate) that is not amenable to structural characterization by single-crystal X-ray diffraction is also presented. On the theme of exploring the time evolution of crystallization pathways, the recent development and application of in situ solid-state NMR techniques for mapping time-dependent changes that occur in the solid phase during crystallization processes are discussed. Finally, the article contemplates the prospects for deriving a fundamental physicochemical understanding of crystal nucleation processes, which is identified as perhaps the most significant challenge in structural chemistry in the next few decades.