Design,Synthesis And Properties Of Hypochlorite Fluorescent Probe Based On Hydropyridine-assisted Amido-to-nitroso Oxidation Reaction

Hypochlorite（ClO^-）is an important reactive oxygen species produced by the reaction of hydrogen peroxide with chloride ions catalyzed by peroxidase,which has the function of killing multiple pathogens and maintaining immune balance.Excessive concentration of Cl O^-will affect the host physiology,and even cause many diseases such as atherosclerosis,lung injury,rheumatoid arthritis and cancer.Among various methods for analyzing and detecting Cl O^-,fluorescent molecular probes are widely used to monitor detect Cl O^-levels in living cells or tissues due to their advantages such as good selectivity,high sensitivity,simple operation and good biocompatibility.Therefore,the development of novel hypochlorite fluorescent molecular probes is considered of great interest in the field of chemistry and sensing.In this thesis,novel hypochlorite fluorescent probes（A4 and B3）were designed by combination of the hydropyridine-to-pyridine and amido-to-nitroso reaction,and the novel recognition mechanism for hypochlorite by the ortho-vinylhydropyridine-assisted amido-to-nitroso oxidation reaction was reported for the first time.The structures of probes（A4 and B3）were confirmed by standard spectral analysis,and its optical properties and application were also investigated,and the details are as follows:In chapter 2,（E）-2-（4-bromo-3-nitrostyryl）quinoline（A2）with extendedπ-conjugation was prepared by Knoevenagle condensation between the starting 2-methylquinoline（A1）and4-bromo-3-nitrobenzaldehyde,followed by nucleophilic substitution with2-pyridylacetonitrile and reduction reactions of nitro to synthesize（E）-2-（4-hydropyridine-3-aminostyryl）quinoline（A4）containing ortho-vinylhydropyridine of the amino group.The results showed that the fluorescent probe A4 had high selectivity for hypochlorite（UV blue-shift,color change from yellow to colorless,fluorescence quenching at642 nm）,fast response time（1.6 s）and low detection limit（77.8 n M）in CH₃CN/PBS=3/7（v/v）solvent system.The sensing mechanism for hypochlorite by the ortho-vinylhydropyridine-assisted amido-to-nitroso oxidation followed by conversion of hydropyridine to pyridine was finally confirmed by the ¹H NMR titration,LC-MS and spectral analysis.Moreover,the A4-loaded paper strips were prepared and successfully used to the“Naked-eyes”detection of hypochlorite.In addition,the quenching of fluorescence signal of the probe with increase of water content was investigated.In chapter 3,using 1,8-naphthalimide as the fluorophore,3-amino-4-hydropyridine-1,8-naphthalimide derivatives（B3）as novel hypochlorite probe was synthesized through the nucleophilic reaction in 4-position with 2-pyridylacetonitrile followed by nitro reduction in3-position of the 1,8-naphthalimide.The results showed that the fluorescent probe B3 had high selectivity（UV blue-shift,color change from red to colorless,fluorescence quenching at626 nm）,fast response time（1.2 s）and low detection limit（36.0 n M）in CH₃CN/PBS=1/9（v/v）solvent system.The sensing mechanism for hypochlorite by the ortho-vinylhydropyridine-assisted amido-to-nitroso oxidation followed by conversion of hydropyridine to pyridine was finally confirmed by ¹H NMR titration,mass spectrometry and spectral analysis.Moreover,the B3-loaded paper strips were prepared and successfully used to the“Naked-eyes”detection of hypochlorite.In addition,the response of probe B3 to water content and its application in biological cell imaging were further investigated.