Design,Synthesis,and Its Application Research Of Three Small Molecule Fluorescent Probes

As one of the thiol compounds in cells,glutathione（GSH）is closely related to physiological and pathological processes in living organisms.In recent years,hydrazine（N₂H₄）and aluminum have been widely used in various fields such as aerospace,materials,and medicine,which also pose a certain threat to human health and ecological environment.Therefore,the detection of GSH in biological organisms and hydrazine and aluminum in the ecological environment is of great significance.Fluorescence analysis has the characteristics of fast response,high sensitivity and selectivity,and non-destructive in situ detection.This method usually uses various fluorescent probes,and small molecular fluorescent probes are important members of them.Many reported fluorescent probes are based on traditional fluorophores,but these probes mostly emit short wavelengths and have small Stoke’s shift,which limits their applications in vivo imaging.Dicyanofluorenone is an emerging fluorophore with high quantum yield,strong photostability,and large Stoke’s shift;Xanthene is another emerging fluorophore that has good photostability and a rigid structure.In addition,both of them have a D-π-A structure that is easy to modify.Therefore,it is necessary to develop fluorescence probes that can detect the above analytes based on these two fluorophores.The present study is based on the outstanding performance of dicyanofluorenone fluorophore and xanthene fluorophore.By regulating the molecular structure of both fluorophores,three fluorescent“off-on”probes were synthesized.The spectral properties of these probes were investigated and they were respectively used to detect GSH,hydrazine,and Al³⁺.Furthermore,the luminescence mechanism and response mechanism of the three probes towards analytes were studied.The following research work was mainly conducted:1.A highly selective and sensitive near-infrared fluorescence probe NIR-A for detecting N₂H₄ was synthesized based on dicyanofluorenone fluorophore.Fluorescence signal gradually increased with the increase of N₂H₄ concentration,making it suitable as a fluorescent enhanced probe for detecting N₂H₄.When the N₂H₄concentration was within the range of 10-100μM,there was a good linear relationship between the fluorescence emission intensity and hydrazine concentration,and the detection limit（LOD）was as low as 4.72μM.Finally,this probe was successfully used to detect hydrazine in water samples.The detection mechanism for N₂H₄ was also studied,and the experimental results showed that it was due to the elimination reaction and nucleophilic addition.2.The near-infrared fluorescence probe for detecting GSH is an effective tool for studying the mechanisms of various diseases.A near-infrared fluorescence probe QX-DNS was designed and synthesized which can detect GSH.The O-S bond can be specifically cleaved by thiol groups,causing the sulfonic acid group to leave in the form of SO₂,while the amino acid thiol group is located on 2,4-dinitrobenzene,releasing a"quinoline xanthene"fluorescent group to restore fluorescence.This probe has a low detection limit,good selectivity,and anti-interference ability.In addition,the good biocompatibility of this probe enables it successful application in cell imaging and semi quantitative determination of exogenous and endogenous GSH in cells.3.A fluorescent probe X-AP was synthesized based on Xanthene fluorophore.Due to the photoinduced electron transfer（PET）effect,the probe is non-fluorescent.After adding Al³⁺,it can coordinate with the phenolic oxygen atom,imine nitrogen atom,and ether oxygen atom of the probe,inhibiting the PET process and enhancing the fluorescence emission.The probe has a low detection limit,good selectivity,and has been successfully applied for the detection of Al³⁺in actual samples.