Synthesis And Properties Of Fluorescence Sensors Based On ESIPT Diarylethene Compounds

Currently,flourescence sensor as a kind of analysis technology have been widely explored and applied.This technology not only enables rapid ananlysis and detection,but also qualitative and quantitative detection of the analyte.However,the early developed fluorophores are prong to aggregation-induced quenching（ACQ）,which leads to limited application prospects and is detrimental to the development of fluorescence sensors.Until the concept of aggregation-induced emission was proposed,which provides a new ideal for the development of fluorescence sensors.In the fluorescent organic materials,the diarylethene photochromic compounds have received extensive attention and application due to their special opening-closing properties and good fatigue resistance,thermal stability and rapid response to light.The combination of photochromic units and functional fluorephores to consutruct to achieve dual detection and light control sensors has become a common method.Based on the above,it’s an inevitable trend to combine their respective advantages to a synthesize a photochromic fluorescences sensors with AIE performance.In the mechanisim of fluorescence sensor,which based on the excited state intramolecular proton transfer（ESIPT）has the advantage of sensitive detection,good selectivity and large Stockes shift,but also face some disadvantages such as short wavalengths emission and ACQ,the AIE phenomenon also overcome the shortcoming of ESIPT fluorescence sensors.They can cooperate with each other on the basic of exerting their respective advantages by combined two mechanisms.Therefore,this thesis is dedicated to designing and synthesizing photochromic fluorescent sensors based on the dual mechanism of AIE and ESIPT.The spectroscopic properties,metal ion sening of the three novel diarylethene compounds and the detailed mechanism obtained are studied.The specific content of the paper is as follows:1.The first chapter introduced the basic properties of diarylethenes and the research progress in the sensor filed in recent years;Explains the excited state intramolecular proton transfer（ESIPT）process and the research progress of fluorescence sensors based on ESIPT.2.In Chapter 2,a new diarylethene 1o was synthesized by combine the photochromic unit with pyrazine-2-carboxamide.Compound 1o shows long（keto）and short（enol）dual-wavelength weak emission in a series of polar solvents,but with the increase of the water volume fraction of the system,strong ESIPT emission（keto）is observed near 580 nm,which also leads to the aggregation of molecules and promotes the occurrence of the ESIPT process.The solid show orange fluorescence under 365 nm UV light.Meanwhile,1o single-identified Al³⁺in acetonitrile solution,and the limit of detection（LOD）was calculated to be 16.6 n M.Moreover,the Al³⁺in several water samples was detected using the sensor with high accuracy by standard addition method.3.In Chapter 3,a diarylethene derivative 2o has been synthesized by attaching a photochromic core to a sulfadiazine moiety.2o showed orange fluorescence under365 nm UV light in solid state.It is also observed dual emission spectrum correspond to the enol and keto formsin a series of solvents.In CH₃CN-H₂O system,the fluorescence emission intensity reached the maximum when the water fraction（f_w）was 70%.2o showed high selectivity to Zn²⁺in methanol solution.The complex ratio of 2o to Zn²⁺was detedmined to be 1:1,and the LOD was calculated to be 50.5 n M.A variety of water sample experiments showed 2o has the potential to be used in the actual environment to detect Zn²⁺.4.In chapter 4,a new diarylethene 3o was synthesized with4-amino-N-（8-aminoquinoline）as the functional fluorophore and diarylene unit.Stockes shift of 3o was 189 nm under the excitation wavelength of 350 nm and when under the 365 nm UV light,3o showed red fluorescence in solid state.The compound showed weak excited state intramolecular proton transfer（ESIPT）based fluorescence in a series of polar solvents and their binary mixtures with water.However,when the water fraction in solutions was above 50%,a strong orange ESIPT emission at～633nm was found,which originated molecules aggregate and ESIPT.3o can recognized Zn²⁺and Cd²⁺in acetonitrile solution and can distinguished them,the combination of3o with Zn²⁺and Cd²⁺was studied,the LOD was calculated to be 50.4 n M and 40,4n M,respectively.Moreover,the water sample experiment shows that 3o can be effectively applied to the detection of Zn²⁺and Cd²⁺in multiple water sample.