Multicolor AIE-active photoswitches with improved fatigue resistance by introducing asymmetric photoactive units

Abstract

Small-molecule photoswitches can be transformed into dual-mode solid-state photoswitches that can be suitable for surface/interface-involved applications by rational structural modification of conventional photochromic molecules. Current solid-state photoswitches are either prone to photochemical side reactions that make them poor in fatigue resistance or it is difficult for them to achieve multicolor photochromism and fluorescence switching. Herein, we first designed and synthesized three AIE-active tetraarylethene-based photoswitches containing two photoactive thiophene units, and by comparing their anti-fatigue and photoswitching properties, we found that the tetraarylethene containing one 2,5-dimethylthiophene photoactive unit has comparable fatigue resistance and photoswitching performance to those containing two photoactive 2,5-dimethylthiophene units, and both of them are much better than that containing two photoactive thiophene units without methyl groups in terms of their fatigue resistance. This design strategy of asymmetric tetraarylethene photoswitches not only solves the problem of poor fatigue resistance of previous tetraarylethenes, but also provides a convenient and feasible route to realize multicolor photoswitches by changing the conjugated structure of the photoactive units. Based on this strategy, we further designed and synthesized three more tetraarylethene-based photoswitches with different conjugated structures. These three photoswitches can realize multiwavelength-controlled multicolor photochromism in solution, and they also have fluorescence switching properties in thin films. These properties allow them to be used in recyclable multiwavelength-controlled colorful photoprinting. This study not only provides the design strategy of asymmetric diarylethene-based photoswitches, but also allows the convenient realization of multiwavelength-controlled multicolor photoswitches.