Design, Synthesis And Properties Study Of Small Molecular Fluorescent Probes Based On Common Fluorescence Dyes

Fluorescent probes which can transfer the molecular recognition events into thefluorescent signal are indispensable tools in various fields of modern science andmedicine, such as clinical diagnostics, biotechnology, molecular biology,biochemistry, materials science, analytical and environmental chemistry. Thecommon dyes like coumarin, rhodamine, BODIPY and cyanine due to their goodphotophysical properties and biological activation including high fluorescentquantum yields, good light stability and biocompatible, have been widely used asfluorophores in fluorescent probes construction. With the development offluorescence spectroscopy and fluorescence imaging technology, the merits offluorescent probes in the analytical fields like real-time and spatial discriminationdetection made fluorescent probes become ideal tools for science research. So, It isof great significance to construct much more kinds of fluorescent probes using thesecommon dyes. In this paper, fluorescent probes for thioureas, mercury ions, sulfuranions and fluoride anions have been constructed using coumarin, rhodamine,BODIPY and cyanine as fluorophores respectively. The concrete contents are asfollows:A method to design fluorescent probes with high selectivity based on the doublefunctional group transformation strategy were found in order to deal with problem oflow selective probes constructed by the single functional group transformationstrategy. Based on that strategy, the first fluorescence turn-on probe for thioureashad been developed by introduced both carbonyl group and bromide atom intocoumarin dye. The probe exhibited high sensitivity and selectivity toward thioureaswith a detection limit of2.8×10-7M. Moreover, the probe could be employed tomonitor thiourea in both water and soil samples. The mechanism study shown thatthe probe taken Hantzsch reaction with thioureas to form thiazole compounds viadouble functional group transformations made fluorescence enhance. From above,the strategy should be much more useful to construct other more fluorescence probeswith high selectivity.Based on the thiophilic and π-philic properties of Hg2+, A new irreversiblefluorescence turn-on Hg2+probe have been designed and easily synthesized byintroduced new receptor of Hg2+into rhodamine dye, which was composed of thiolatom and alkyne. The probe elicited a large fluorescence enhancement (140fold) and exhibited high selectivity, low detection limit, and fast response to Hg2+. In addition,the mechanism study shown that the interaction between probe with Hg2+involved inboth coordinated and mercury-mediated catalyzed processes. The successful Hg2+imaging in living cells indicated that the probe has a great potential application.Based on the thiophilic and π-philic properties of Hg2+, A new reversiblefluorescence turn-on Hg2+probe have been designed and easily synthesized byintroduced novel receptor of Hg2+into rhodamine dye, which was composed of thiolatom and alkene. The reversible probe can detect Hg2+in the near pure aqueousmedium at neutral conditions, and exhibited high selective and sensitive to Hg2+witha detection limit of27.5nM. In addition, the probe also can detect Hg2+in livingcells in a reversible way. The reversible nature of the probe will find interestingbiological applications and the novel Hg2+receptor presented herein will be usefulfor construction of other types of reversible fluorescent Hg2+probes.In order to solve the problem of hard regulated fluorescent signal of cyaninedye, the displacement approach was proposed to regulate the fluorescent signal ofcyanine dye. The first NIR fluorescent probe for sulfide anions has been constructedby linked cyanine dye and copper ligand8-aminoquinoline with a piperazine linker.The probe in aqueous media showed high sensitivity and high selectivity towardsulfide anions, and work well in a wide pH range. Given the fact that it is relativelychallenging to switch off the fluorescence of NIR dyes, a transition-metal-baseddisplacement strategy may open an avenue for the development of NIR fluorescentsensors for a wide variety of anion targets with a significant NIR fluorescenceturn-on response.Based on the ICT character of the coumarin and BODIPY dyes, a new hybriddye, coumarin-BODIPY, was designed and synthesized. Furthermore, a novelratiometric fluorescent sensor for fluoride anions based on the newcoumarin-BODIPY platform was developed. The probe exhibited a large red shift(88nm) in absorption, a drastic ratiometric fluorescent response (I472/I606=17.4)and highly selective to fluoride anions. Density function theory and time-dependentdensity function theory calculations were conducted to rationalize the opticalresponse of the probe. The unique ICT character of the coumarin-BODIPY platformwill be widely employed to construct a wide variety of ratiometric fluorescentsensors based on the ICT signaling mechanism.