Click Annulation of Pseudo[2]rotaxane to [2]Catenane Exploiting Homoditopic Nitrile <i>N</i>‑Oxide

A mild annulation reaction of a propargyl-terminated pseudorotaxane with a homoditopic stable nitrile <i>N</i>-oxide enabled the efficient synthesis of catenanes consisting of not only dibenzo-24-crown-8-ether (DB24C8) but also dibenzo-30-crown-10-ether (DB30C10) as a wheel component. A dynamic ¹H NMR study showed the highly enhanced mobility of the components of the DB30C10-based [2]catenane due to the enlarged wheel cavity

Fluorescence Control of Boron Enaminoketonate Using a Rotaxane Shuttle

The effect of rotaxane shuttling on the fluorescence properties of a fluorophore was investigated by exploiting fluorophore-tethered [2]rotaxanes. A fluorescent boron enaminoketonate (BEK) moiety was introduced in a rotaxane via transformation of an isoxazole unit generated as a result of an end-capping reaction using a nitrile <i>N</i>-oxide. The rotaxane exhibited a red shift of the fluorescence maximum along with a remarkable enhancement of the fluorescence quantum yield through wheel translation to the fluorophore