Visible light-induced single bond rotation in azoarenes triggered by self-sensitized oxidation

Controlled molecular motion is a cornerstone of both biological function and artificial dynamic systems. While light-induced isomerization of double bonds is well-established, selective rotation around single bonds without concurrent double bond isomerization remains largely unexplored. Here, we present a class of chalcogen-substituted azoarenes that undergo light-induced N-C single bond rotation, independent of N[double bond, length as m-dash]N isomerization. This rotation is triggered by self-sensitized photooxidation of an ortho-tellurium center, which switches the preferred binding site of a β-hydroxy group from the azo unit to the tellurium σ hole. Experimental evidence from UV/Vis and NMR spectroscopy, supported by quantum chemical calculations, confirms the light-induced rotation and its complete reversibility upon chemical reduction. Importantly, the process is accessible under both UV and sunlight. This study establishes a new mechanism for directing molecular motion, offering a versatile strategy for designing photo- and redox-responsive molecular switches.