Diarylethenes

Diarylethenes are a class of photochromic organic compounds defined by two aryl rings connected by an ethene (C=C) moiety. In the open form, the molecule is typically colorless. Upon irradiation with ultraviolet light, it undergoes a reversible cyclization that forms a closed-ring isomer in which a new bond between the aryl rings extends conjugation. The closed form is usually colored, absorbing in the visible region. Reversion to the open form can be induced with visible light or by thermal back reaction, returning the compound to its colorless state. The pair of forms constitutes a molecular switch.

Properties commonly highlighted in diarylethenes include high fatigue resistance (many switching cycles without degradation), strong contrast between the two forms, and good thermal and photostability. The switching wavelengths and kinetics are tunable by modifying the aryl groups, electron-donating or withdrawing substituents, and steric constraints, enabling customization for specific applications. Diarylethenes often exhibit fast response times and high quantum yields for photoisomerization.

Applications span molecular switching in photoresponsive materials, optical data storage, smart polymers, liquid-crystal devices, sensors, and nanoscale systems. Their robust fatigue resistance and chemical versatility have made them a leading platform in organic photochromism, with ongoing research aimed at expanding accessible wavelengths, improving solid-state performance, and integrating them into functional devices.