Electrooxidation-Induced Reverse Switching in Azobenzene-Based Photoswitches

Photoswitches, which reversibly switch between isomeric forms upon light exposure, offer promising applications in optical computing, photoresponsive materials, and molecular energy storage. Efficient and controllable back-isomerization is essential for practical applications and can be achieved electrochemically. In this study, we explore how electrochemical oxidation governs the back-conversion of the azobenzene-based photoswitch 4,4′-(diazene-1,2-diyl)bis( N, N ′-diethylaniline) (A-AZO). Combining in situ photoelectrochemical infrared reflection absorption spectroscopy with density functional theory calculations, we show that A-AZO undergoes reversible two-step oxidation, forming singly and doubly oxidized species (A-AZO 1+ and A-AZO 2+ ), with the positive charge primarily localized on the nitrogen atoms of the amino groups. Photochemically, ( E )-A-AZO isomerizes to its ( Z )-form. Upon electrochemical triggering, the oxidized ( Z )-A-AZO x + species act as catalytic intermediates that accelerate the back-conversion to the ( E )-isomer. This autocatalytic reaction proceeds with high selectivity and requires minimal external energy input, making it particularly attractive for energy-efficient switching in molecular systems.