Controllable Versatility in a Single Molecular System from Photoisomerization to Photocyclization

Abstract Cyanostilbene is a typical photoresponsive group with multiple photochemical reactions. However, it is still challenging to achieve multiple photochemical reactions and versatility in the same molecular system at one wavelength excitation. The cyanostilbene‐based molecule synthesized in this work can undergo photoisomerization and photocyclization in sequence under continuous illumination at 365 nm in solution. This process is demonstrated by nuclear magnetic resonance, high‐resolution mass spectroscopies, and single crystal X‐ray diffraction. The fluorescence intensity of the solution gradually increases by more than ten times with the extension of the illumination time due to the formation of a photocyclization product with a high fluorescence quantum yield. Based on this interesting phenomenon, the multifunctional applications of this system are presented. This provides a design idea for multifunctional molecules via photochemical reactions.