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-AZO1+ and A-AZO2+), 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-AZOx+ 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.