photoisomerizable

Photoisomerizable refers to molecules that can undergo isomerization upon absorption of light. In such compounds, irradiation promotes electrons to excited states, enabling changes in the geometry or connectivity of the molecule, resulting in distinct isomers with different shapes and properties. The process often involves rotation around a bond or cyclization, and the isomerization can be reversible, allowing cycling between forms upon exposure to different wavelengths or light/dark cycles. Thermal relaxation can restore the original isomer over time.

The most studied photoisomerizable systems include azobenzenes (trans to cis isomerization around the azo double bond), stilbenes, spiropyrans (ring-opening to merocyanines under UV light), and diarylethenes (reversible closed/open forms with high fatigue resistance). Other motifs include quantum yields, wavelengths, and environmental effects. Such systems can be driven by UV or visible light depending on substituents; some are designed to operate with visible light to minimize damage.

Applications of photoisomerizable compounds span molecular switches, data storage, photoresponsive polymers, liquid-crystal devices, sensors, and actuators. In materials, photoisomerizable units can alter polarity, shape, or packing, enabling controllable stiffness, permeability, or optical properties. Limitations include photodegradation, incomplete conversion, and dependence on wavelength and temperature, which influence performance and stability.