Enhancing tetraphenylethene cyclization as photoswitch

Abstract

AbstractTetraphenylethene (TPE), a star building block with promising aggregation‐induced emission, has received much interest. Given that its intramolecular Woodward‐Hoffmann cyclic intermediate instantaneously converts back to the original state within several picoseconds, the essentially photochromic characteristic of TPE is little investigated. Achieving a visible photocyclization of TPE is still an unsolved issue and considered as the bottleneck in the further advancement of applications. We report a strategy of attaching carbonate ester onto the TPE skeleton (TPE‐4C) to enhance TPE photocyclization stability. As demonstrated, the incorporated cholesteryloxycarbonyloxy substituents in TPE‐4C can increase the energy barrier for cycloreversion, thereby exhibiting extremely thermal stability of photocyclic intermediate upon UV irradiation, prolonging its lifetime from 63 picoseconds to 46 s by 7.2 × 1011‐fold. The photoinduced cyclization of TPE‐4C could be monitored with naked eyes, and the photocyclization/cycloreversion is achieved by turning on/off UV light along with a relative fatigue resistance. Encapsulation of TPE‐4C into the liquid crystal can induce a striking phase transformation (achiral↔chiral), which can be applicable to encode optical information. Employing carbonate ester into the TPE unit plays a vital role in enhancing the unprecedented TPE photocyclization stability, providing a toolbox to allow TPE‐based photocyclization to be visually monitored.