A lot to unpack: a decade in high Z′ crystal structures

Abstract

Crystal structures that form with more than one molecule in the asymmetric unit (Z′ > 1) are a fascinating and important, if overlooked, aspect of crystal engineering. With the recent publication of the results of the ‘seventh blind test of crystal structure prediction’ the challenges that these structures present and the questions they provoke for the prediction and design of crystalline solids are brought sharply into focus. This article documents developments in the study of high Z′ structures over the last ten years and shines a spotlight on the most extreme and intriguing examples from recent publications. The lessons learned from these studies will inform future crystal engineering and design efforts as strides are made to work around the computational expense inherent in the prediction of structures with large asymmetric units.