Development Of Benzocoumarin-based Fluorescent Probes And Their Applications In Analytical Chemistry

Coumarin is a chemical compound in the benzopyrone chemical class that can be found in many natural species.Coumarins are provided with variety of biological activities and excellent photophysical properties.Coumarin compounds are widely used in the development of fluorescent dyes and molecular probes because of their high fluorescence quantum yield,good light stability and biological compatibility.However,the traditional coumarin compounds have short excitation and emission wavelengths,which hinder their applications in biomedicine and fluorescent imaging.In the continuous research and application process,various kinds of theπ-extended or fused coumarin structure of coumarin derivatives have been developed.Among them,benzocoumarin show superior photophysical properties in the bioimaging applications.Moreover,a large two-photon absorbing ability,the longer excitation and emission wavelengths,high photostability,and high chemical stability are the key advantageous features of benzocoumarin derivatives.In this study,we prepared a 7-diethylaminocoumarin and 1-indanone-fused benzo[c]coumarin fluorescent dye CI.And new fluorescent probes for detecting hydrazine and hypochlorous acid was designed by using CI as the scaffold.The content of this paper is as follows:Chapter 1.The classification,synthetic,photophysical properties and application researches of benzocoumarins were summarized.Chapter 2.A 7-diethylaminocoumarin and 1-indanone-fused fluorescent dye（CI）was developed.CI was superior to traditional coumarins in terms of bathochromic shift in absorption and emission maxima(λ_abs/λ_em=518/598 nm in ethanol).To illustrate its value,we rational designed a new hydrazine-selective fluorescent probe by the judicious anchoring of CI to malononitrile to form CI-DCV.Upon mixing with hydrazine,the dicyanovinyl group of CI-DCV was converted to the corresponding hydrazone,which inhibited the intramolecular charge transfer within the probe,thereby affording remarkable blue shifts in the absorption and fluorescence spectra.The fluorescence intensity of the reaction solution increases linearly with hydrazine concentration（0-7μM）.And the detection limit was determined to be 8.6 nM.The proposed probe shows high selectivity toward hydrazine over other structural analogs and reductive species and can be applied in hydrazine detection in a variety of samples.Chapter 3.Development of a ratiometric fluorescent probe based on benzocoumarin for hypochlorous acid.The 2-mercaptoethanol was employed to protect the carbonyl group of CI in the design of probe CI-ClO.The protection of carbonyl group interruptedπ-conjugated system of CI.Therefore,the probe CI-ClO shows short absorption and emission wavelengths,which similar to the traditional coumarin(λ_abs/λ_em=427/507 nm in ethanol).The probe CI-ClO reacts with hypochlorous acid to deprotect the oxathiolane group to release the carbonyl group,which would lead to the red shift of absorption and emission wavelengths.The results show that the fluorescence intensity ratio（I608/I528）of the reaction solution is a function of hypochlorous acid concentration（0-14μM）.And the detection limit was calculated to be 99.0 nM.In addition,the probe CI-ClO with a good selectivity for hypochlorous acid was successfully applied in fluorescence imaging.