Structure correlation and dynamics in crystals – a tribute to Hans-Beat Bürgi

Abstract

Crystal structures are not static; they contain a wealth of information about dynamics and reactivity of molecules and extended solid materials. On the one hand, dynamic properties are related to the atomic and lattice vibrations in crystals, so that an accurate description of both atomic displacement parameters and diffuse scattering are important for crystallographic experiments. Disorder in crystals may be also related to dynamic behaviour, and the description of dynamic behaviour renders the determination of thermodynamic properties of crystals possible. On the other hand, series of related crystal structures can be understood as snapshots along a pseudo-reaction pathway, which relates 'static' crystallography to chemical reactivity.These aspects of structural science have been major themes in Hans-Beat Bu ¨rgi's scientific career spanning nearly 60 years. Structure correlation, disorder, and the dynamics of atoms and molecules in crystals remain important but sometimes still underrated fields of structural chemistry today. For those reasons, we have taken the opportunity to highlight these topics in this thematic special issue dedicated to Hans-Beat Bu ¨rgi on the occasion of his 80th birthday this year.Hans-Beat Bu ¨rgi's university education in the Chemistry Department of the Federal Institute of Technology (ETH) Zu ¨rich culminated in the completion of his PhD research in 1969 under the supervision of Jack Dunitz. After a two-year postdoctoral stint with Lawrence (Larry) Bartell at the University of Michigan, focusing on structure determination in the gas phase by electron diffraction, Hans-Beat returned to single-crystal X-ray diffraction and to the laboratory of inorganic chemistry at the ETH for his habilitation work leading a small independent research group. In this period between 1971 and 1979, many of the ground-breaking studies that determined Hans-Beat's career were undertaken, such as the development of the structure correlation idea (Bu ¨rgi, 1973) of which the highly cited concept of the Bu ¨rgi-Dunitz angle of nucleophilic attack at carbonyls is part (Bu ¨rgi et al., 1974). The cover illustration of this special issue shows Hans-Beat at the blackboard in Zu ¨rich in 1974, explaining the concept to a guest researcher from Japan.His substantive position for nearly 30 years was Professor and Director of the Laboratory of Chemical and Mineralogical Crystallography at the University of Bern (Fig. 1). During this time, Hans-Beat established himself as one of the leading international authorities of X-ray crystallography. Many of his achievements are described and reflected in this special issue, and he has described them in substantial detail in a recent essay in the Israel Journal of Chemistry (Bu ¨rgi, 2017), so we have not attempted to list or summarize them here. In his post-retirement roles as an Emeritus Professor in Bern and a permanent academic guest at the University of Zu ¨rich, Hans-Beat continues as an active researcher who does not miss a single day in the office.