Multiple yet Controllable Photoswitching in a Single AIEgen System

Seeking new methods
to obtain elaborate artificial on-demand photoswitching
with multiple functionalities remains challenging. Most of the systems
reported so far possess only one specific function and their nonemissive
nature in the aggregated state inevitably limit their applications.
Herein, a tailored cyanostilbene-based molecule with aggregation-induced
emission characteristic was synthesized and was found to exhibit efficient,
multiple and controllable photoresponsive behaviors under different
conditions. Specifically, three different reactions were involved:
(i) reversible Z/E isomerization
under room light and thermal treatment in CH3CN, (ii) UV-induced
photocyclization with a concomitant dramatic fluorescence enhancement,
and (iii) regio- and stereoselective photodimerization in aqueous
medium with microcrystal formation. Experimental and theoretical analyses
gave visible insights and detailed mechanisms of the photoreaction
processes. Fluorescent 2D photopattern with enhanced signal-to-background
ratio was fabricated based on the controllable “turn-on”
and “turn-off” photobehaviors in different states. The
present study thus paves an easy yet efficient way to construct smart
multiphotochromes for unique applications.