Developing Coumarin-based Fluorescent Probes For Sensing Bisulfite Anion And Thiophenol

Bisulfite（HSO₃^-）is widely used as an antioxidant,antimicrobial agent and enzymatic inhibitor for foods,pharmaceutical products and beverages.However,it has been shown that HSO₃^-may be toxic in high doses,triggering asthma attacks,allergic reactions and so on.Thiophenol is widely used in production of pesticides,pharmaceuticals,polymers and dyes.The exposed thiophenol liquid or vapor may induce central nervous system damage,increased respiration,muscle weakness,vomiting,coma and even death.Fluorescent probes are very sensitive,low cost,easily performed,capability of real-time monitoring and versatile detection.Therefore,the development of fluorescent probes for rapid and specific detection of thiophenol and HSO₃^-has attracted much attention.Coumarins are attractive starting materials for constructing fluorescent probes due to their high fluorescence intensity,excellent solubility,efficient cell permeation,and ease of preparation.In this thesis,coumarin-based fluorescent probes were designed and synthesized for highly selective and sensitive detection of HSO₃^-and thiophenol.The main contents are summarized as follows.1.Inspired by Guo’s work（Chem.Commun.2013,49,2637）,we designed MCH by incorporation of the 7-hydroxycoumarin and hemicyanine dye platforms.A nucleophilic addition reaction occurred between HSO₃^-and MCH,resulting in inhibition against the intermolecular charge transfer（ICT）process of MCH along with its hypochromic-shifted emission.Therefore,MCH worked as a colorimetric and ratiometric fluorescent probe.It manifested the following advantage for sensing HSO₃^-selectively:favorable selectivity,high sensitivity（LOD=10.6 n M）and fast response rate（2 min）.By virtue of its benzo[d]thiazol-3-ium moiety,this probe could efficiently localize to mitochondria of He La cells to monitor local change in HSO₃^-levels.2.We developed a coumarin-based probe CA for sensing thiophenol in term of its specific reaction with 2,4-dinitrophenyl ether.This probe was characterized of a replacement of hydroxyl with phenoxyl and introduction of an electron-withdrawing formyl group in the 7-and 3-positions of 7-hydroxycoumarin,respectively.Its sensing mechanism involved a nucleophilic substitution with thiophenol to release free fluorophore 3,which harbored the strong“push-pull”effect to effectively promote an ICT process and a“Turn-on”fluorescence response.CA displayed high selectivity,favorable sensitivity（LOD=6.55 n M）and appropriate response time（10 min）for sensing thiophenol and was successfully applied for its imaging in living cells.