A building-block design for enhanced visible-light switching of diarylethenes

Current development of light-responsive materials and technologies imposes an urgent demand on visible-light photoswitching on account of its mild excitation with high penetration ability and low photo-toxicity. However, complicated molecular design and laborious synthesis are often required for visible-light photoswitch, especially for diarylethenes. Worse still, a dilemma is encountered as the visible-light excitation of the diarylethene is often achieved at the expense of photochromic performances. To tackle these setbacks, we introduce a building-block design strategy to achieve all-visible-light photochromism with the triplet-sensitization mechanism. The simply designed diarylethene system is constructed by employing a sensitizer building-block with narrow singlet-triplet energy gap (ΔE ST ) to a diarylethene building-block. A significant improvement on the photochromic efficiency is obtained as well as an enhanced photo-fatigue resistance over those under UV irradiation. The balance between the visible-light excitation and decent photochromism is thus realized, promoting a guiding principle for the visible-light photochromism. Development of light-responsive materials imposes a demand on visible-light photoswitching but this is often achieved at expense of photochromic performance. Here the authors use a building-block design to achieve a diarylethene all-visible-light photoswitch with improved photochromic efficiency and enhanced photo-fatigue resistance.