Design,Synthesis,Structure-property Relationship And Properties Of Azine-based AIE Fluorescent Sensor Molecules

In the past two decades,aggregation-induced emission（AIE）has attracted wide attention due to its good application prospect.The AIE properties provides a good platform for the development of luminescent materials,showing a wide range of applications in fluorescence sensors,biological imaging and functional materials.Although many AIE luminogens（AIEgens）with adjustable colors and high quantum yields have been reported,the development of new,easily prepared AIEgens is still an attractive subject.In addition,it is important to study the mechanism of AIE and the structure-property relationship for the synthesis of new AIE sensors.In this thesis,the AIE mechanism,synthetic methods and applications of azine derivatives in recent years are summarized.It is found that azine derivatives are easy to synthesize and some of them have good AIE properties.Therefore,the systematic study of AIE mechanism and structure-property relationship of azine derivatives is helpful to further understand the AIE mechanism of this kind of AIEgens,and provide ideas for the design,synthesis and application of new simple and efficient AIEgens.In view of this,in order to study the easy-to-prepare AIEgens based on azine,this thesis studied the structure-activity relationship,ions recognition properties and functional materials of azine derivative AIEgens:In the first part,a series of azine derivatives（AD1-AD10）were used as models to study the effects of different functional groups,electronic effects and structures on the AIE properties of azine derivatives.The mechanism of AIE was studied by means of single crystal structure analysis and density functional theory（DFT）.The results indicated that the o-hydroxyl-aryl substituted azine derivatives could show good AIE properties.The o-hydroxyl group can form intramolecular hydrogen bond with imine group,which plays a key role in limiting the intramolecular rotation of aryl group.Finally,due to AIE properties,o-hydroxy-aryl substituted azine derivatives can be used as highly effective Al³⁺and Cu²⁺fluorescent chemical sensors under different conditions.In addition,the test strips based on AD10 has been prepared,which can easily detect Cu²⁺in industrial wastewater.In the second part,a long alkyl chain functionalized azine derivative G was synthesized.Firstly,its AIE properties were studied.Due to retention of ortho-hydroxyl group,the G possess AIE properties.The G can detect CN^-in DMSO/H₂O（8:2,v/v）solution in two channels,but its detection sensitivity is not high.While,after assembly G with pillar[5]arene P5,the CN^-detection sensitivity of G can be improved.The assembly mechanism was studied by theoretical calculation.P5 penetrates into the alkyl chain of G,and there are hydrogen bonds（C-H···O）and weak interaction force（C-H···π）between them.Then,the mechanism of G’s recognition of CN^-was studied by theoretical calculation and host-guest ¹H NMR spectra experiment respectively.The results showed that when CN^-was added,the-OH could deprotonate,cause the intramolecular charge transfer,and make its fluorescence“turn on”.After assembly,CN^-has strong bonding ability with the assembly through hydrogen bonding,anion-πand anion-dipole interactions.The electron-rich cavities of pillar[5]arene promote the intramolecular charge transfer of G and improve the sensitivity of CN^-recognition.In the third part,a bipedal quaternary ammonium azine derivative（DNH）is synthesized.DNH can self-assemble into hydrogel（DHN-G）.Because the ortho-hydroxyl group is substituted,the gel has no AIE properties.Interestingly,when fumigated with HCl or CF₃COOH vapors,the gel exhibited an orange-red fluorescence emission.This is due to the binding of the acid proton with the N of DNH,DNH forms intramolecular hydrogen bond,limits the intramolecular rotation of DNH,causes AIE properties,and occurs strong fluorescence emission phenomenon.Subsequent fumigation with NH₃·H₂O will cause the fluorescence quenching,and at the same time,the color of the gel will return to yellow,which is due to NH₃·H₂O capturing protons and destroying the intramolecular hydrogen bond of DNH,so DNH can be used as acid-base stimuli-response material.In conclusion,a series of azine derivatives were designed and synthesized in this thesis,and their AIE properties and structure-property relationship were studied.The results revealed that the o-hydroxyl group played a key role in the AIE performance of the aryl-substituted azine derivatives.Studies on ions recognition indicated that o-hydroxy-aryl substituted azine derivatives possess fluorescence detection ability for Al³⁺and Cu²⁺.In addition,the assembly of pillar[5]arene and functionalized azine can effectively improve the sensitivity of the azine-based sensor for CN^-detection.Finally,the stimuli-response materials based on azine derivatives show response to acid and base.These results have certain application prospect.