Development Of Circular Dichorism And Fluorescence Dual-Modality Fluorescent Probes For Heavy Metal Ions And Analyte Regneration Fluorescent Probes For Formaldehyde

This thesis contains two parts.The first part is the development of fluorescence/circular dichroism(CD)dual-modality probes for multiple heavy metal ions.Toxic heavy metal ions have caused serious harm to the environment and health of humans.The design and development of efficient new multi-component metal ion probes is still one of the hotspots and difficulties in the field of metal ion probes.First,the fluorescence/CD responses of the probe 2-1 towards three heavy metal ions,Ag+,Hg2+ and Cu2+,were studied.It was found that CD signal changes are often opposite to fluorescence signal changes.In other words,fluorescence quenching are often accompanied with the rising of CD signals,and vice versa.Mechanistically,heavy-metal ion-induced C-S cleavage of the thioazolidine ring results in heavy metal ion complexation with with the formed coumarin-imine ligand induced fluorescence quenching and exciton coupling induced CD signal rising.Further metal-ion complexation induced hydrolysis removes the heavy metal complexation and chiral environment of the chromophore,generating fluorescence turn-on response and reduction of CD signals.To study the effect of different substitutions of coumarin fluorophore towards reaction the probe’s fluorescence and CD responses with the three heavy metal ions,the probes 2-2 and 2-3 were designed and synthesized,and their fluorescence and CD responses were studied.It was found that the substitution on the coumarin fluorophore can efficiently modulate the Cu2+promoted coumarin lacton hydrolysis by changing their electron-donating properties.The coumarin-D-penicillamine based probes were the first fluorescence/CD dual-modality system,which can detect and differentiate multiple metal ions.The second part deals with the structure modification of the analyte regeneration fluorescent probe 3-1 for formaldehyde(FA)previously developed in our lab.Formaldehyde(FA)is reactive oxygen specie and metabolite in biological systems,which plays important physiological and pathological roles.Deveolpment of fluorescent probes as chemical tools for their detection is vital for the bioactivity studies.Replacement of the fluorophore led to the design and synthesie anthracene-carboximide based probe 3-3.We also designed and synthesized probes 3-4,3-5,3-6,3-7 and 3-8 via changing the benzyl amine reaction groups to other amino groups.The probes’ fluorescence responses towards FA wer studied.It was found that increase the steric bulkiness of the benzylamine group or introduction of other amino groups can inhibit fluorescence reduction due to formation of aminal,which is favorable for anylte regeneration detection of FA.We also studied the potential CD response of the chiral probe 3-8 for FA.