Design,Synthesis And Properties Of Novel Organic Molecular Fluorescent Materials

Organic fluorescent materials have good fluorescence characteristics,and are widely used in medical research,chemical testing and modern biology.As a molecular sensor,the fluorescent probe has the advantages of high sensitivity,low detection limit,and strong anti-interference in detection.It can be used to analyze and detect various trace elements or harmful substances in the biological environment.The discovery of the phenomenon of aggregation-induced luminescence?AIE?has fundamentally overcome the century-old problem of fluorescence quenching caused by aggregation,and has pointed the way forward for the development of organic solid fluorescent materials.It further stimulated people's interests.This thesis synthesized theirderivativesbasedon7-hydroxybenzoxazinoneand2-?2'-hydroxyphenyl?benzothiazole fluorophores and discussed related applications.The specific contents are as follows:In Chapter 2,2,4-dinitrobenzenesulfonyl?DNBS?as a recognition group was used to modify the fluorescent molecule 7-hydroxy-3-phenylbenzoxazinone.We invented a kind of fluorescent probe PBD that specifically recognizes biothiols.Due to the extremely strong fluorescence quenching effect of the DNBS group,the probe molecule of PBD is almost non-fluorescent.When DNBS specifically reacted with biothiol,the fluorescent molecule 7-hydroxy-3-phenylbenzoxazinone was released,showing extremely strong fluorescence.The fluorescent probe has relatively low detection limits for biothiols(LOD_GSH=14.5 n M;LOD_Cys=17.5 n M;LOD_Hcy=80.0n M),and is with excellent selectivity to competitive species and anti-interference ability.And it has been successfully applied to the detection of biothiols in living cells.In Chapter 3,a series of 2-?2-hydroxyphenyl?benzothiazole?HBT?derivatives with an aggregation-induced emission–excited state intramolecular proton transfer?AIE-ESIPT?dual mechanism was synthesized.We systematically investigated their optical properties in solution,aqueous suspension,and the solid state.The fluorescence properties of these five compounds were highly dependent on the solvent environment.Particularly,DMSO and DMF were found to significantly promote deprotonation of the phenolic hydroxyl and favor fluorescence emission from the phenolic anion.The Keto or Enol forms generally could be transformed to phenolic anions with the aid of base in solution.The results from aggregation-induced emission enhancement?AIEE?and red-shifted AIE clearly illustrated the evolution process of the fluorescence spectra,indicating that the three luminescent species in the solution were transformable.The systematic investigation demonstrated that the desired fluorescence could be generated for HBT derivatives by varying the solvents or adding additives,such as base or water,to the solution.Because of the synergistic effect of AIE and ESIPT,these fluorophores exhibited high solid-state quantum yields and large Stokes shifts.These dyes also featured high photostability and tunable emission spectra covering most of the visible light region.Single crystal studies and theoretical calculations elucidated the luminescent properties.When loaded on filter paper,the HBT-based dyes exhibited high-efficiency fluorescence visualization and reversible solid-state luminescence switching under alternating amine and acid vapor treatments.These dyes were used on banknotes for anti-counterfeiting measures,demonstrating the practical applications of these molecules as fluorescent anti-counterfeiting inks.