Construction And Properties Of Photoresponsive Stiff-stilbene/Cucurbituril-based Supramolecular Assemblies

Stiff-stilbene is an excellent photochromic molecule that undergoes cis-trans isomerization around the C=C double bond under UV irradiation and is often used as an important component of supramolecular photosensitive systems.Cucurbiturils,a frequently-used class of macrocyclic hosts with rigid cavities,can encapsulate positively charged guests or charge-transfer complexes to self-assemble into stable host-guest complexes through electrostatic and hydrophobic interaction.In this paper,we have synthesized two water-soluble stiff-stilbene derivatives as guests to construct two photoresponsive supramolecular assemblies based on stiff-stilbene/cucurbituril,and investigated their photophysical and photochemical properties,and further explore their applications.The specific research content is as follows:1.A reversibly regulated supramolecular assembly has been fabricated from cucurbit[7]uril（host）and water-soluble stiff-stilbene（guest）through host-guest complexation.They could conduct photoisomerization between its（E）-and（Z）-configuration,when irradiated at alternating 311 nm and 385 nm light.The introduction of cucurbit[7]uril resulted in decline ofΦ_E→Z and elevation ofΦ_Z→E of the stiff-stilbene and fluorescence of the supramolecular assembly could be switched on/off upon irradiation with distinct light.Under the conditions of ultraviolet irradiation or the addition of cucurbit[7]uril,the photochromic guest in this photosensitive system can further selectively modulate the G-quadruplex structure.2.Pyridine double bond coupling stiff-stilbene（guest）have been designed and synthesized,and assemble with cucurbit[8]uril to form a[2+2]supramolecular assembly through host-guest interaction.They could conduct photoisomerization between its（E）-and all-（Z）-configuration.The intervention of macrocyclic host cucurbit[8]uril efficiently improves the photochromic guest’s fatigue resistance as well as photoluminescence performance fluorescence intensity（＞40%）and quantum yield（＞0.18）.The stiff-stilbene/cucurbit[8]uril supramolecular assemblies exhibit excellent fluorescence switching properties and are further investigated for their application in high security level anti-counterfeiting of QR code.