Design,Synthesis And Application Of AIE-active Fluorescent Probe Based On Quinoxaline Derivatives

The exploration of the fluorescent probe with solid state emission and AIE(Aggregation-induced emission)performance is developing rapidly in recent years.Thanks to the deep study of the RIR and RIM mechanisms,the design and establishment of AIE molecules can be more effortless and have powerful theoretical support.Aggregation-caused quenching phenomenon is due to the close range between molecules at the solid or aggregation states,where the?-?interaction urges the energy dissipation of the excited state through the nonradiation channels and fluorescence quenching,this phenomenon seriously affected the the sensitivity of the detection system under high concentration,real-time detection and biological cell imaging and so on of most aromatic fluorescent probe.On the one hand,we design and use the simple synthetic method to get some new solid state emission and AIE molecules on the basis of quinoxaline derivatives.On the other hand,we explore the new fluorescent probes in the applications of the detection of biological intracellular pH changes,explosives detection in the air and water environment,high selectivity and efficient recognition of GSH in mitochondria in living cells.Firstly,triphenyl ethylene group was introduced to the quinoxaline derivatives by Suzuki coupling,we design and synthesize two quinoxaline derivatives fluorescence molecules with solid state emission and AIE performance 1a and 1b.When in the mixture solution(PBS/acetonitrile,v/v=9/1),the fluorescence enhancement of 1a and 1b show 8 times and8.3 times compared with the dispersion state in pure organic solvent,respectively.Under the90%glycerin viscosity system,the fluorescence enhanced around 9 times.We employed the electron-withdrawing ability of quinoxaline and the electron donating ability of triphenyl ethylene to get the ICT effect,which can produce different emission wavelength in different polar solvents.The fluorescent emission range from 510 nm to 552 nm.More importantly,the fluorescent nanoparticles of 1a and 1b can efficiently tracking explosives PA(picric acid).After30 minutes of the contact with gas PA,nanoparticles of 1a and 1b showed 57%and 52%quenching extent.Test paper probes can detect 5*10~-66 M PA aqueous solution by naked eye.The application in environmental monitoring to detect explosive PA has been expanded based on the quinoxaline derivatives with AIE performance.Secondly,on the basis of synthetic work of previous part,we firstly get the asymmetric structure GQ by linked triphenyl ethylene and a pyridine ring to the both sides of quinoxaline core,respectively.Then we linked the pyridine ring and dinitrodiphenyl benzyl bromide benzyl ether between the N atoms and bromine by simple into salt reaction to get an AIE molecule GQP,which can locate at the mitochondria and specific identification of glutathione.On the one hand,we can ensure that the molecules will have a good AIE phenomenon from the second part of our experiment.The fluorescent intensity enhanced to 15.5 times when water content is70%in DMSO/water system compared with pure DMSO.And the PL intensity increased 9.3times when the glycerol content reaches 90%under the viscosity system.Interestingly we found GQ also showed AEE fluorescent properties in DMSO/water system when the water content is90%,the fluorescent intensity increased 2.7 times.The solid-state emission of GQP is orange red at 584 nm.And the solid-state emission of GQ is green at 517 nm also suggests that salt reaction can effectively reduce the energy gap to get red shift;On the other hand,Pyridine salt is a mitochondrial localization group,as well as the dinitrobenzene part is a typical recognition site to identify the amino acid groups.After the literature research we learned that this recognition groups can selectively identify GSH by extend the length of a benzene ring.GQP in PBS/DMSO(v/v=1:1)system can be successful in detecting GSH with high selectivity and high sensitivity,the fluorescent intensity increased 12.5 times after reaction with 10 equivalent of GSH.The mechanism of detection of GSH is nucleophilic substitution reaction between GSH and dinitrobenzene part,will lead the identify groups completely broken off and generated GQ structure,blocking the PET process and enables the fluorescence enhancement.The cell imaging experiments also prove that the molecules can achieve successful in the recognition of mitochondrial GSH with fluorescence enhancement.It offered valid reference to design biological sensing applications in this field based on quinoxaline derivatives fluorescent probesFinally,based on the previous work we introduced benzothiazole group to the 8 replace site of BODIPY through acetylenic bond to get fluorescent probe H.The huge space steric of benzothiazole can limit the molecular?-?interaction to get the solid emission and AIE effect BODIPY.The phenolic hydroxyl of benzothiazole group can occur deprotonation in alkaline conditions and identify pH effectively.In DMSO/glycerol,the fluorescence intensity of H increased 3.4 times when70%glycerol content.The solid state emission of H at 607 nm and present a strong orange red fluorescence with the absolute quantum yield is 4.1%,which is higher than that BODIPY fluorescent probes with solid state emission reported in recent literatures.The pH sensor system of H is PBS buffer:DMSO(v/v=1:9).Along with the pH value increased from 4.5 to 9.8,the ratio value of fluorescence intensities of the emission peaks of H at 528 and 484 nm is reduced from 12.29 to 1.02,the ratio value of fluorescent probe with internal standard emission is suitable to detect pH more accurate and sensitive.We use nigericin to adjust the intracellular pH,H successfully applied in Hela cells.The cytotoxicity experiments also show that the pH probe can be used for a long time due to the low toxicity.