RESUMEN
Invited for the cover of this issue are Ben L. Feringa and co-workers at the University of Groningen. The image depicts an autumn forest with the five molecular switches from our study cycling between their two isomers in the sunlight. Read the full text of the article at 10.1002/chem.202400482.
RESUMEN
The norbornadiene/quadricyclane (NBD/QC) photoswitch pair represents a promising system for application in molecular solar thermal energy storage (MOST). Often, the NBD derivatives have very limited overlap with the solar spectrum, and substitution to redshift the absorption leads to a decrease in the gravimetric energy density. Dimeric systems mitigate this factor because two switches can 'share' a substituent. Here, we present five new NBD dimers with red-shifted absorption spectra. One dimer features the most red-shifted absorption onset (539â nm) and a significantly red-shifted absorption maximum (404â nm) for NBD systems reported so far, without compromising thermal half-life. Promising properties for high-performance MOST applications are demonstrated, such as high absorption onsets reaching 539â nm, and energy densities of 379â kJ/kg, while still maintaining long half-lives of the metastable isomer, up to 23â hours at 25 °C.