Design,Synthesis And Application Of Coumarin And Quinoline-based Fluorescent Probes

A variety of ions,small molecules and proteins exist in living systems.The production,distribution and fluctuation of these active species play important roles in maintaining metabolism or causing various diseases.For example,hypochlorous acid?HOCl?as a key component of immune system,can also lead to oxygen stress due to the excessive generation.Hydrogen sulfide?H₂S?as a gasomediator,involved in myocardial contractility,vascular tone,and insulin secretion.Recently,the qualitative and quantitative analysis of the visualization of intracellular active species by fluorescent probes has been wildly utilized in chemistry,medicine and biology.Therefore,it is of great significance to develop new fluorescent probes with excellent performance.This work is mainly divided into five parts:Chapter 1 The significance of fluorescent probe and the typical mechanism of recognition were briefly introduced in this part.The development of fluorescent probes of reactive oxygen species,hydrogen sulfide,biothiols,metal and pH in recent years was also discussed,so as to confirm the research content of this paper.Chapter 2 A 7-diethylaminocoumarin based fluorescent probe CMOS was synthesized for detection of hypochlorous acid and cysteine/homocysteine.The1,3-oxathiolane was chose as the recognition moiety of CMOS,which displayed high sensitivity?LOD=21 nM?,selectivity and fast response?t<10 s?in the presence of HOCl.The resultant of the reaction of CMOS and HOCl is CMAC,which is able to selective detection of cysteine and homocysteine.The recognition progress of CMOS to HOCl and cysteine/homocysteine displayed on-off-on fluorescence response.The recognition mechanism was confirmed by HPLC-MS experiments.Furthermore,the probe CMOS was applied to monitoring the HOCl and cysteine/homocysteine in living cells with low cytotoxicity.Chapter 3 A two-photon ratiometric fluorescent probe OS-BC was designed and characterized for investigation of HOCl.The probe was constructed by a benzocoumarin fluorophore and the recognition moiety of oxathiolane.In the presence of HOCl,the recognition moiety was oxidized to acetyl,the fluorescence emission peak shift from 540 nm to 573 nm.The ratiometric detection of OS-BC to HOCl displayed high sensitivity?LOD=96.3 nM?,selectivity,short response time?t<5 s?and pH independence.The response mechanism was confirmed by the HPLC-MS experiments.The probe OS-BC was able to monitor HOCl,which produced by the reaction of H₂O₂ and Cl^-with the catalysis of myeloperoxidase.OS-BC was successfully applied for ratiometric detection of exogenous and endogenous HOCl in living cells under two-photon excitation mode.Chapter 4 A 7-diethlaminocoumarin-based fluorescent probe CMOH was synthesized for detection of Cu²⁺and S^2-.CMOH displayed high sensitivity?detection limit=3.2 nM?and selectivity to Cu²⁺with complex CMOH-Cu²⁺formation via a 1:1 binding mode.In the presence of S^2-,the CMOH-Cu²⁺recovered to CMOH and CuS,which acted as a sensitive probe with a low detection limit of11.4 nM.This‘‘on-off-on''process can be accomplished within 1 min and repeated at least 5 times.The recognition mechanism was confirmed by ¹H NMR experiments and density functional theory calculation.The probe CMOH exhibited good solubility,low cytotoxicity and can be used as a suitable tool to detect changes of Cu²⁺and S^2-in living cells.Chapter 5 A 4-methoxy quinoline-based fluorescent probe DQPH has been developed for ratiometric detection of pH fluctuation.Upon altering the pH from 4.5to 9.0,the emission spectra exhibit a large hypsochromic shift?57 nm?and the ratio of fluorescence intensity(F_{531 nm}/F_{588 nm})changes from 0.3 to 1.4 and a linear pH variation range of 6.3-8.0 with a pK_a value of 7.18.The ratiometric response is attributed to the protonation-activable resonance charge transfer?PARCT?process,which has been proved by ¹H NMR and NOESY experiment.This probe displayed good solubility,low cytotoxicity,anti-interference capability and reversible pH sensing.Furthermore,DQPH was successfully applied for monitoring pH changes in living cells.