Synthesis And Recognition Properties Of Carbazole-based Fluorescent Probe

Recently,fluorescent analysis method is widely used in chemistry,molecular biology,environmental science,medicine and other fields for its high sensitivity,good selectivity,widely response range of linearity,simple operation,low cost,real time monitoring and so on.So it is more and more attractive to synthesize and build high sensitivity,good selectivity fluorescent probes.Carbazole derivatives are often used to construct ICT fluorescent probe as a fluorophore for its huge conjugated systems and active intramolecular charge transfer effect(ICT).In this article,we designed and synthesized three carbazole-based ICT fluorescent probes for pH and thiol detection.The main research contents are as below:Chapter 1:This chapter is a brief introduction of fluorescent probe techniques and carbazole-based fluorescent probe.The composition and recognition mechanism of fluorescent probe,structure characteristics of carbazole derivatives,and the recent research progress of carbazole-based fluorescent probe are introduced detailed.Chapter 2:A ratiometric fluorescent pH probe 2-(9-ethylcarbazole-3-vinyl)-benzothiazole(Probe-1)is facilely developed by vinyl bridging of 9-ethylcarbazole and benzothiazole,which is a useful fluorescent probe for strongly acidic pH sensing.The pH titration experiments indicate remarkable fluorescence enhancement effect and an emission red-shift of 87 nm with pH decreasing from 7.00 to 1.00.The solution color also changes from light blue to orange under a UV lamp illumination.A pKa value of 1.62 and a good linearity in the pH range of 1.23-2.10 indicate that the probe can be used in quantitative fluorescence imaging under strongly acidic condition.In addition,Probe-1 exhibits high selectivity,good sensitivity,excellent photostability and reversibility for pH sensing.Furthermore,this probe is successfully applied to imaging extremely acidic pH in Escherichia coli cells without influence of autofluorescence in biological systems.Chapter 3:A novel fluorescent probe 2-benzothiazole(9-ethylcarbazole-3-yl)-hydrazone(Probe-2)has been reported for strongly acidic and basic pH sensing.In pH titration experiments,the fluorescence emission peak has a red-shift from 424 nm to 446 nm and the fluorescence intensity gradually strengthened with pH changes from 7.40 to 1.64,while a red-shift from 424 nm to 445 nm also find and the fluorescence intensity gradually weakened with pH ranges from 7.40 to 13.01.Through sigmoidal and linear fitting plots of fluorescence intensity with pH values,a pKa value of 2.73 and linear response range of 1.23-2.10 are obtained under acidic condition,and a pKa value of 11.29 and linear response range of 10.41-12.43 are obtained under basic condition.The confocal fluorescence imaging in Escherichia coli cells proves that the probe can also be used for pH detection at biological systems.Chapter 4:This paper reports a highly selective and sensitive fluorescent probe(Probe-3)through blinding 9-ethylcarbazole and maleimide group for glutathione(GSH)detection.Under gradually addition of GSH,the fluorescent intensity of probe strongly increases at 377 nm in the system of DMSO:water = 1:3(v/v,HEPES buffer solution,pH 7.40,10 mM)and the solution reveal a dramatic color change from non-fluorescence to blue under a UV lamp illumination.The calibration curve is linear(R2 = 0.9978)in the concentration range from 2?M to 18?M with a detection limit of 0.05?M.Besides,the selective and interferential experiments further demonstrate that it is an excellent probe for GSH detection.The reaction mechanism is also conjectured by ESI-MS and 1H NMR analysis.