Synthesis And Properties Of Coumarin-fused BODIPY NIR Fluorescent Dyes

Fluorescent dyes have been widely used in chemistry,biology,medicine and other fields.Especially,near-infrared fluorescent dyes have significant advantages in biological imaging applications because of their strong tissue penetration and lack of interference from spontaneous background fluorescence of biological tissues.However,so far,most of the reported near-infrared fluorescent dyes have emission wavelengths in the near infrared region,while absorption wavelengths are not in the near infrared region,or their Stokes shift is relatively small,and absorption and emission overlap is relatively large.These defects seriously limit the application of fluorescence imaging technology in the field of biological imaging.Therefore,the development of near-infrared fluorescent dyes with excellent photophysical and photochemical properties and large Stokes shift plays an important role in promoting the application of fluorescence imaging technology in the fields of biology and medicine.In this thesis,aiming at the defect of small Stokes shifts in existing near-infrared fluorescent dyes,based on the mother nuclear framework of boroborofluoropyrrole（BODIPY）with excellent photophysical and chemical properties,a series of coumarin-fused BODIPY near-infrared fluorescent dyes with large Stokes shifts were constructed using the strategies of paracyclic derivation and linear derivation,and their photophysical properties were studied in detail.The research contents are as follows:1.A series of coumarin-fused BODIPY near-infrared fluorescent dyes with large Stokes shifts were designed and synthesized.Using a paracyclic derivation strategy,coumarin fluorophores with good biocompatibility and large Stokes shifts were introduced into the BODIPY mother nucleus with excellent photophysical and chemical properties.C-BDP-CH3,a large Stokes shift coumarin-fused BODIPY parent nucleus,was constructed.In order to expand the conjugated system,C-BDP-CH3 was transformed into C-BDP-CHO by oxidation of PCC,and then the conjugated system of parent molecule was expanded by Knoevenagel condensation reaction between C-BDP-CHO and compound with activeα-hydrogen atom using linear derivation strategy.Six near-infrared fluorescent dyes（C-BDP-1～C-BDP-6）with large Stokes shifts were constructed,and their structures were characterized by ¹H NMR,¹³C NMR and MS.2.The photophysical properties of coumarin-fused BODIPY near infrared fluorescent dyes were studied.By testing the UV-visible absorption spectra and fluorescence spectra of C-BDP near infrared fluorescent dyes in different solvents,it is proved that the absorption and emission of these dyes are in the near infrared region,and the Stokes shift is relatively large,which is suitable for biological imaging applications.3.The application of near-infrared fluorescent dye C-BDP-5 with stable photophysical and chemical properties in polarity detection is studied.By testing the fluorescence spectra of C-BDP-5 in solvents of different polarity,it is found that the fluorescence intensity of C-BDP-5 in solvents of low polarity is very high,but low in the large polar solvent.The fluorescence intensity of C-BDP-5 decreases by nearly 63 times from the small polar toluene solution to the large polar glycol solution,accompanied by a certain degree of redshift.There is a good linear relationship between the fluorescence intensity of C-BDP-5 and the polarity parameterΔf of Lippert Mataga（R²=0.9887）,and the polarity detection of C-BDP-5 is not affected by the viscosity microenvironment and other analyzers,so it has the potential to be applied in the polar test in vivo.