Study On The Design,Synthesis And Properties Of Stimuli-responsive Tetraphenylethylene-based Compounds

Stimuli-responsive fluorescent materials are regarded as"smart"material that can respond to external stimuli and have aroused many researchers’interest recently becaused of their wide application in fluorescent probes,bioimaging,smart materials,etc.However,the design and development of compounds with multiple stimulus-response properties,compounds with dynamic stimulus-response properties,and compounds with stimulus-response properties in both solid and liquid state are still a big challenge.In this thesis,TPE was employed as the molecular skeleton to develop new stimulus-responsive fluorescent materials through reasonable molecular design and their fluorescent properties,stimuli-responsive mechanisms and practical applications were investigated detaiedly.The main contents of this paper are as follows:1 A photo/force-responsive TPE-based Schiff base compound（TPENOMe）was simply synthesized and its properties,mechanism and practical application were detailedly investigayed.By slowly evaporating the dichloromethane/n-hexane mixed solution of TPENOMe,two different crystals of TPENOMe were obtained,which exhibited completely different photochromic and fluorescent properties.The fluorescence of the bulk crystal（TPENOMe-a）was very weak but it exhibited reversible photochromic behavior.The fluorescence of the needle-like crystal（TPENOMe-b）was very strong;however,it did not exhibit photochromic properties.Detailed investigations demonstrated that the different photoinactivation ways resulting from significantly different crystal packing styles was responsible for the unprecedented various properties.In addition,the stimulation of external mechanical force can also change its photochromic and fluorescent properties.TPENOMe-a can be used as an inkless rewritable paper with self-erasing and reusable properties.They can be also used as a reusable data encryption material.2 A water and force-responsive tetraphenylethene-based thiazole compound（TBTNO₂）was designed and synthesized by introducing the AIE and the twisted intramolecular charge transfer（TICT）mechanism into one molecule.TBTNO₂exhibited interesting"on-off-on"optical switching properties with significant fluorescence changes under the stimuli of water.TBTNO₂ is highly sensitive to trace water in organic solvents,therefore,it was employed as a fluorescent sensor for detecting trace water in organic solvents.In addition,TBTNO₂ exhibited reversible mechanochromism in the solid state.3 A series of tetraphenylethylene-based benzothiadiazole derivatives(TPEB-o-NO₂,TPEB-m-NO_2,and TPEB-p-NO₂)were designed and synthesized by adjusting the substituent position of nitro group to investigate the influence of substituent positions on their emission properties.The difference of substituent positions of nitro group can result in changes of intramolecular conjugation,thus leading to different photophysical properties.Due to the combined action of AIE and TICT,the three compounds exhibited solvatochromic effects and“on–off–on”optical switch behavior under stimuli of water.Moreover,TPEB-m-NO₂ and TPEB-p-NO₂ were successfully employed as fluorescent sensors for detecting trace water in organic solvents.4 A multi-stimulis-responsive and dynamic stimulis-responsive tetrastyrene thiazole（TPEB-B）compound was designed and synthesized which exhibited reversible and dynamic stimulis-responsive fluorescencent properties under stimuli of water,acid-base and force,respectively.The fluorescene of the solution gradually blue-shifted from weak aquamarine blue to intense blue emission with enhanced fluorescence intensity after injecting large amount of water into its THF solution.Such dynamic fluorescence change was caused by the gradual formation of large aggregates of TPEB-B molecules.In addition,TPEB-B exhibited reversible acidichromism behavior due to protonation and deprotonation of nitrogen atoms on the thiazole ring.Moreover,TPEB-B also exhibited reversible mechanochromism.Its emission color can be reversibly changed between and yellowish green under stimuli of grinding and fuming.TPEB-B can be used in anti-counterfeiting due to its multi-stimuli-responsive behaviors.5 A multiple dynamic stimulis-responsive tetraphenylethene-based Schiff base（TPESB）was designed via a combination of AIE and excited state intramolecular proton transfer（ESIPT）mechanism,which exhibits absorption/fluorescence dual-mode color changes induced by water and zinc ion.When a little water was injected,the color and emission color of the solution gradually changed form colorless to yellow and weak red to strong yellow,respectively,showing a dynamic fluorescence change.A new inkless rewritable paper was developed by employing TPESB as imaging layer and water as ink,which can be used in anti-counterfeiting and information security.In addition,TPESB can also used as a colorimetric/fluorescent dual-channel sensor for Zn²⁺ions.Additionally,TPESB can be successfully applied for sensing of Zn²⁺in living cells due to its low cytotoxicity.6 A dynamic stimuli-responsive tetraphenylethene-substituted Schiff base（TPENOCN）was synthesized and its application in inkless rewritable paper and anti-counterfeiting were investigated.The emission color of TPENOCN exhibited dynamic changes from yellow to blue with an enhanced fluorescent intensity under stimuli of water.Detailed investigation revealed that the radiation channel of TPENOCN can be regulated from low energy state emission to high energy state emission by water stimulation.Theoretical and experimental investigations indicated that such changes were resulted from the formation of intermolecular hydrogen bond between TPENOCN and water.Furthermore,a new inkless rewritable paper was successfully developed by employing TPENOCN as imaging layer and water as ink,which exhibits greatly potential application in security writing/printing,multilevel anti-counterfeiting and data storage.This paper contains 131 figures,14 tables and 328 references.