Unraveling the Mutual Impact of Photoswitchability and Emission Behavior in Luminescent Arylazopyrazoles

Photoresponsive molecular systems uniting light-controlled switching and luminescence are of great interest for next-generation optoelectronic materials. However, azoarenes in which both photoisomerization and emission are triggered and modulated under a single wavelength remain exceedingly rare. To address these challenges, arylazopyrazoles were combined with heteropentacene luminophores to yield fluorescent photoswitches. In-depth investigations were conducted to understand the concurrent photoluminescence and isomerization in solution, including temperature-dependent NMR studies, measurements of absolute photoluminescence quantum yields, and excited-state lifetimes. The findings were supported by quantum chemical calculations of the excited-state processes, which revealed the interplay between emissive and isomerization pathways, leading to a design concept for fluorescent photoswitches based on arylazopyrazoles. Finally, the application of these multi-responsive emitters was examined by embedding them into liquid crystalline and 3D-printed materials to investigate the effects of temperature, photoswitching, and order on photoluminescence ─ a pathway to next-generation photoresponsive materials.