Visible‐Light‐Driven [2+2] Photocycloaddition in Self‐Assembled State for Time‐Resolved Information Encryption

Abstract Achieving time‐resolved information encryption is crucial for advanced functional materials but remains a formidable challenge. Photoresponsive supramolecular assemblies have gained attention as promising candidates in this area. This work presents a unique strategy that employs α‐cyanostilbenes to construct photoresponsive assemblies which enable finely regulating fluorescence color and photoresponse kinetics, facilitating effective time‐resolved information encryption. Three α‐cyanostilbenes 1–3 are designed by the combination of electron donor 3,4‐ethoxylene dioxythiophene appended benzaldehyde with electron acceptor phenylacetonitrile with different substituents. All three compounds undergo reversible Z/E isomerization in CH₃CN under 420 and 254 nm light irradiation. Interestingly, while in CH₃CN/H₂O with high water content (95%), these compounds are found to be able to self‐assemble into spherical assemblies with reduced molecular distances. Remarkably, upon exposure to 420 nm visible light, [2+2] cycloadditions occur within the assemblies, exhibiting distinct photoresponse kinetics and fluorescence variations due to the formation of cycloaddition products, confirmed by ¹H NMR spectroscopy, high‐resolution mass spectrometry, and single crystal structures. Furthermore, their unique fluorescence color changes and photoresponse kinetics demonstrate the potential applications in time‐resolved information encryption and hydrogel‐based photo‐patterning. This research offers a compelling strategy for designing visible‐light‐driven fluorescent switching materials for high‐level information encryption and beyond.