We had Professor Matthieu Sollogoub of Sorbonne University for a seminar last Friday and were treated to an outstanding lecture on cyclodextrin functionalization and utility. This foray included many aspects of catalysis, materials science, and drug delivery. Of course, you probably know where cyclodextrins are used the most: they are the main component of Febreze, a remarkable innovation to eliminate bad odour. Apparently, the reason cyclodextrins (there are several types, depending on the cavity size) cost on the order of 4 euros per kilogram is because of Febreze. The hydrophobic cavity of these molecules is destined to encapsulate a range of chemicals, including those that are volatile and offensive in smell. In the interest of time, I will not draw the whole molecule of a cyclodextrin (check it out here), but I will say this: the amount of insightful stuff Prof. Sollogoub has been able to find in this area is quite remarkable. My favourite part of the presentation was when he described the way in which azide-functionalized cyclodextrins stick to each other and form higher order assemblies on the nanoscale. The driver here is the interaction between adjacent azide functionalities. I am afraid I do not know other examples that convincingly demonstrate similar through-space interactions between two resonance forms of a functional group. This finding, characterized crystallographically, was the highlight for me and I encourage you to read the Angewandte paper below.