Synthesis And Properties Of Coumarin And Rhodamine Fluorescent Probes Containing Tetrahydroquinoline Donor

Fluorescence detection method has the advantages of simple operation,high sensitivity,low detection cost,and can be carried out real-time and non-destructive in vitro and in vivo detection.Particularly,near-infrared(NIR)fluorescence detection has been proved to be more suitable for living systems due to its deeper tissue penetration,lower background interference and minimum tissue damage.Coumarins and rhodamines are widely used fluorophores for fluorescent probes.However,traditional coumarins and rhodamines exhibit emissions in the visible region(<600 nm)with small Stokes shift(<60 nm),which greatly limit their bioimaging applications.Therefore,it is of great significance to modify their structures,to make their fluorescence emissions to the NIR region,and to increase their Stokes shifts.In this thesis,using the ICT fluorescence mechanism of coumarins and rhodamines,we introduced tetrahydroquinoxaline as their donor group,successfully red-shifted the fluorescence to the NIR region,and solved the problem of small Stokes shift.The specific work is as follows:1.In chapter 1,we reviewed the development of fluorescent probes based on coumarins and rhodamines.2.In chapter 2,a new coumarin fluorophore NIR-IC was synthesized by introducing tetrahydroquinoxaline as donor group into 3-[2'-benzothiazolyl]-7-diethylamine coumarin imine.The results showed that NIR-IC had near-infrared emission(Em:652 nm)and a large Stokes shift(128 nm).At the same time,a fluorescent probe NIR-IC-H2S was synthesized which could recognize hydrogen sulfide quickly(<5 min)and be used to bioimaging in cell and mouse in vivo.3.In chapter 3,a new water-soluble fluorophore CO-NH2 was developed by introducing tetrahydroquinoxaline as a donor group into 3-amino-7-diethylamine coumarin.Our results showed that fluorescence emission was red-shifted to 587 nm(closed to NIR),as well as Stokes increased to 177 nn.Moreover,we developed a CO-NH2 based fluorescence probe CO-DNS for the detection of thiophenol,which had been applied successfully in water samples and cell imaging.Besides,compared with the reported synthesis route for salicylaldehyde,a key intermediate for CO-NH2,our synthesis showed various significant advantages such as stable starting material,simple operation,and higher yield.4.In chapter 4,we developed a new fluorophore PEG-IC by introducing water-soluble group-methyl carbitol(PEG)into NIR-IC.The results showed that NIR-IC exhibited emissions in the near-infrared region(Em:642 nm),and also had a large Stokes shift(122 nm).Then,we further developed fluorescence probe PEG-IC-PhSH for quick(<3 min)and specific detection of thiophenol in cell,zebrafish,and mouse.5.In charter 5,three new fluorophores RO-1/2/3 were developed by introducing tetrahydroquinoxaline as a donor group into rhodamine Rh Q-H.The results showed that all these fluorophores had near-infrared emission(Em>680 nm)and a large stokes shift(>99 nm).Then,a probe RO-ONOO-was synthesized which could react with ONOO-quickly(<2 min),and it was amazing that RO-ONOO-could also be used as a pH probe which revealed the potential of this probe for dual detection.Finally,we solved the stability of the key intermediate tetrahydroquinoxaline-6-ol by way of salt formation.6.In chapter 6,a lysosome-targetable pH probe RO-2-Lyso was developed by introducing PEG acetyl into RO-ONOO".The results showed that both RO-ONOO-and RO-2-Lyso showed excellent stability and were applied for bioimaging in cells successfully.7.In chapter 7,RO-CIO-was designed and synthesized by using RO-2 as fluorophore and thiolactone as a reaction site.It was successfully applied for fluorescent imaging of endogenous HClO in HeLa cells.8.The chapter 8 summarizes the whole thesis and looks forward to the future research.