Design,synthesis And Properties Of Solid-state Fluorescent Switches Based On Fulgide Derivatives

Solid-state fluorescent switches have attracted more and more attention because of their broad applications in optical memory,such as anti-counterfeiting inks,optical writing and erasing and biological imaging.Fulgide(FUL)and its derivatives with obvious visual color and fluorescence change under alternating irradiation of ultraviolet light and visible light in solution,are regarded as efficient fluorescent switches and promising candidates for the application of optical memory owing to their high thermal stability and fatigue resistance.However,solid-state fluorescent switches based on fulgide and its derivatives still rarely reported since they have no fluorescence or weak fluorescence in solid state due to the aggregation caused quenching(ACQ)effect from the planar structure of fulgide moiety.Recently,aggregation induced emission(AIE)provided a new strategy to overcome the ACQ effect,which AIE fluorogens usually enhance emission in solid state.In this paper,two solid-state fluorescent switches were synthesized by covalently connecting AIE molecules and photoswitch molecules,and their photophysical properties were characterized and analyzed.The specific research contents are as follows:1.Synthesis,properties and applications of solid-state fluorescent switches based on fulgide derivativesThe fulgide group was covalently connected to the classic AIE molecule tetraphenylethylene(TPE)group,and an effective reversible solid-state fluorescent switch TPE-FUL was constructed via Suzuki coupling reaction.TPE-FUL exhibits reversible changes in color and fluorescence in the solid state under alternate irradiation of ultraviolet light and visible light.Experimental and theoretical studies indicated that the fluorescence of the open TPE-FUL(O-TPE-FUL)comes from the local excited state(LE)of the TPE moiety,while the fluorescence quenching of the closed O-TPE-FUL(C-TPE-FUL)is caused by intramolecular charge transfer(ICT)from the TPE moiety to the FUL moiety.At the same time,we also demonstrate the application of TPE-FUL molecules in anti-counterfeiting inks,optical erasing and information encryption.These application results show that the combination of fluorescent switch groups and AIE fluorescent groups is an effective strategy for constructing solid-state fluorescent switches.2.Influence of substituents on the properties of solid-state fluorescence switches of fugide derivativesTetraphenylethylene(TPE)with two methoxy groups was covalently attached to the fulgide group to construct an effective reversible solid-state fluorescent switch TPEOMe-FUL via Suzuki coupling reaction.TPE-OMe-FUL powder changed from yellow to black quickly under ultraviolet light irradiation,and the green fluorescence was quickly quenched.While it can return to the original yellow powder and green fluorescence under visible light irradiation.Theoretical calculations indicate that due to the increase of the intramolecular donor-receptor effect,the closed TPE-OMe-FUL(CTPE-OMe-FUL)intramolecular charge transfer ICT effect is enhanced,which increases the conversion rate of O-TPE-OMe-FUL to C-TPE-OMe-FUL.TPE-OMe-FUL molecules can also have application in anti-counterfeiting inks,optical information storage and information encryption.