Encapsulation drives visible light isomerisation in azobenzene photoswitch

 A new supramolecular capsule helps trigger the isomerisation of azobenzene with visible light. For the first time, the system enables full conversion to the metastable Z form, unlocking new possibilities for photoswitches, including for applications in energy storage and non-invasive medical treatments.

Azobenzenes are the most popular photoswitches – molecules that change shape upon exposure to light. Usually, ultraviolet light triggers the transformation between the stable E and metastable Z isomers, but this reaction faces several hurdles, including problems associated with selectivity and efficiency. ‘The core problem for azobenzenes is E to Z isomerisation, because the E [form] gets activated at wavelengths that activate the Z form,’ explains Nathalie Katsonis, an expert in photoswitches and supramolecular chemistry at the University of Groningen, in the Netherlands, who wasn’t involved in the work. ‘It’s a super original [study] that proposes a concept to overcome this limitation,’ she adds.