Host–guest complexation of dithienylethene photoswitches with cucurbit[8]uril leads to photoresponsive binding pairs with picomolar affinity in water.

The use of external stimuli to control the binding kinetics in supramolecular systems is of critical importance for the development of advanced molecular machines and devices. In this work, a study focused on the kinetics of a water‐soluble host‐guest system based on cucurbit[8]uril and two dithienylethene (DTE) photoswitches is reported. It is shown that for the DTE guest comprising two anionic sulfonate side arms appended to pyridinium moieties, the formation/dissociation of the pseudorotaxane structures is slowed down by more than 100000‐fold with respect to its bipyridinium analogue. The decrease in ingression rate leads to the emergence of a competitive metastable product with the open DTE isomer that has an important influence in the overall binding kinetics. Moreover, the host‐guest dissociation kinetics is demonstrated to be approximately 100‐fold slower for the closed DTE isomer (t1/2=107 h vs. t1/2=1.2 h for the open isomer) allowing control over the dissociation rate with light.

Production of long polymer chains with iron oxidation and storage activity, built from protein nanocages using a click chemistry approach.

Photoresponsive binding kinetics was achieved in cucurbit[8]uril‐dithienylethene host‐guest complexes. This work demonstrates that, in the presence of a competitor guest (in purple), the host‐guest dissociation kinetics is approximately 100‐fold slower for the closed (green) than for the open (yellow) dithienylethene isomers (t 1/2=107 hours vs. t 1/2=1.2 hours), allowing control over the dissociation rate with red/NIR light. More information can be found in the Full Paper by A. Jorge Parola, N. Basílio, et al. (DOI: 10.1002/chem.202100974).