Reversible Photoluminescence Control of Azobenzene Crystals by Light and Heat Stimulation.

Stimulus‐responsive photoluminescence (PL) materials have attracted attention because of their broad applicability in recording, switching and sensing devices. However, the development of PL materials controllable by a light stimulus remains a challenging task. Here, we demonstrate novel organic crystals of a naphthalene‐functionalized azobenzene derivative (NA) that exhibit reversible PL properties upon light and heat stimulation. The azobenzene derivative exhibits aggregation‐induced emission (AIE) in the orange PL region upon crystallization. Upon photoirradiation, the crystal transforms into an aggregate with low crystallinity via trans‐to‐cis photoisomerization. Therefore, the PL color changes from orange to yellow when the orderly aggregated NAs are converted into randomly aggregated NAs. Furthermore, the original orange PL can be recovered upon heating and cooling the photoirradiated crystal as a result of cis‐to‐trans thermal back‐isomerization. [ABSTRACT FROM AUTHOR]