ECM20 reception in the courtyard of the oldest building of the Zagiellonon University where Copernicus studied.The 32nd Erice course in Crystal Engineering entitled Strength from Weakness: Structural Consequences of Weak Interaction in Molecules, Supramolecules and Crystals emphasized the study of interactions not just by crystallography, but also by techniques ranging from gas phase electron diffraction, IR and NMR to theoretical techniques. Important points were raised about the meaningfulness of comparing measurement of parameters obtained by different techniques, given the fact that different techniques measure different things. Sometimes there is an obvious difference such as the difference between a time averaged structure and a single 'freeze frame' snap shot of a molecule in motion or the differences between theoretical calculations calculated for an idealized case at absolute zero and experimental results obtained at ambient temperatures for a molecule in a real system. The highlight of the meeting was the lively, (sometimes heated!) debates on the nature of hydrogen bonds, especially the existence of 'blue shifted hydrogen bonds' (Hobza) and the classification of strong hydrogen bonds (Gilli), and on the virtues or otherwise of theoretical versus experimental techniques.
Charlotte Broder, U. of Durham