Synthesis Of Reactive Targeted Sulfur Dioxide Derivative Fluorescent Probes Using Aromatic Rings As Fluorophores And Their Applications In Food

SO₂ is a food additive allowed at home and abroad and is generally added to food in the forms of sodium sulfite,sodium metabisulfite,sodium bisulfite,low sodium sulfite,potassium metabisulfite,etc.,playing a role in color protection,preservative,bleaching and antioxidant in food industry.However,studies have confirmed that excessive SO₂ can cause not only respiratory diseases such as asthma,tracheitis and emphysema,but also closely related to cardiovascular diseases,for instance,ischemic heart disease and cardiac arrhythmia.Therefore,many countries strictly control the residual threshold limit for SO₂ in food.Accordingly,it is of significant relevance for the detection of SO₂ in food.Some traditional methods for SO₂ detection are relatively mature,however,compared with these methods,fluorescent probes have irreplaceable advantages such as high sensitivity and selectivity,low detection limits,simple operation and on-site testing.Recently,many studies have been reported on the detection of SO₂ by fluorescent probes.In this thesis,based on the excellent fluorescent properties of aromatic（fused）rings,a series of reactive fluorescent probes for targeted detecting SO₂ with aromatic（fused）rings as fluorescent groups were designed and synthesized,and their spectral properties were investigated:1.Two ratiometric fluorescent probes CTM and CTDM with a large conjugate structure were designed and synthesized by organic combination of malononitrile and fluorene fluorophore.When HSO₃^-nucleophilically attacks the unsaturated C=C double bond of both the probes,the conjugation systems of probe CTM and CTDM are interrupted,resulting in solution colors change from yellow or orange to colorless,respectively,and achieving the specific recognition of HSO₃^-.Probes CTM and CTDM exhibit both ratiometric and colorimetric detection characteristics of HSO₃^-with high selectivity and sensitivity.The detection limits for CTM and CTDM to HSO₃^-are 6.09×10^-4 M and1.49×10^-3 M,respectively.Moreover,probe CTM was successfully applied to detect HSO₃^-residues in white sugar,brown sugar and rock sugar,showing superior detection performance.2.The ratiometric fluorescent probe DY was designed and synthesized utilizing 11,12-Dihydroindolo[2,3-a]carbazole as the fluorescent moiety and benzoindole salt as the acceptor.Probe DY realized the detection of HSO₃^-by using unsaturated carbon-carbon double bonds as the recognition site.When probe DY interacts with HSO₃^-,the conjugate system of the probe is broken and the solution color turns from purple to colorless,achieving the detection of HSO₃^-.Probe DY can respond to HSO₃^-within 20 seconds.Besides,the detection limit of probe DY for HSO₃^-was 8.5×10^-4 M.3.Two D-π-A type fluorescent probes DTY and DTYS with colorimetric characteristic were constructed for the detection of HSO₃^-by connecting a rigidly structured 11,12-Dihydroindolo[2,3-a]carbazole and benzoindole derivatives via thiophene asπ-bridge.Similar to probe DY,DTY and DTYS recognize HSO₃^-also by using the C=C double bond as the recognition site while Michael addition reaction as recognition mechanism.HSO₃^-attacks the C=C double bond of the probes,the ICT process of the probes are interrupted,leading to the solution colors fade and achieving recognition by naked eyes.Probe DTY and DTYS can respond to HSO₃^-at physiological p H,and selectivity experiments show that probe DTY and DTYS have high selectivity and sensitivity for HSO₃^-detection with detection limits of 0.71 n M and 6.17 n M,respectively,which are among the few targeted HSO₃^-probes that can reach nanomolar levels.Furthermore,the probe DTY has been successfully applied to the detection of HSO₃^-in tap water and wine.