Investigation On Hydrazine Fluorescence Probes Based On Chalcone Skeleton And Cyclization Mechanism

As a dangerous carcinogen,hydrazine is closely related to human health and the environment.Therefore,the detection of hydrazine in trace amounts has attracted wide attention from scientists.Chalcone,as a type of fluorescent compound,has good luminescence properties,low biological toxicity,and reaction sensitivity,which is caused by the nature of its carbon-carbon double bond group being vulnerable to nucleophilic attack.At the same time,based on the excellent luminescence properties and low biological toxicity of coumarin and pyrene,as well as the mechanism of dihydropyrazole formation by addition and cyclization of chalcone as the recognition site with hydrazine,three types of fluorescent materials including coumarin chalcone derivatives,hydroxycoumarin chalcone derivatives and pyrene chalcone derivatives,were designed and synthesized in this thesis.The recognition effect of the above compounds on hydrazine,the recognition mechanism,the influence of the molecular terminal substituents on the recognition effect and the application in the field of hydrazine sensing were comprehensively explored.（1）Coumarin chalcone derivatives（2）Hydroxycoumarin chalcone derivatives（3）Pyrene chalcone derivativesIn the coumarin chalcone system,it was found that both the designed compounds 2 and 3can realize the colorimetric ratio identification of hydrazine.By comparing the recognition effects of the three compounds on hydrazine,it was found that the electron-withdrawing substituents on the benzene ring of the compounds can effectively promote the recognition of hydrazine.Among them,compared with compound 2,compound 3 shows a lower detection limit（0.1 ppb,0.003μM）,a large fluorescence ratio change(I₄₆₅/I₅₇₅,1265 times before and after titration),a faster response rate,and a wide range of p H working range（3.0-12.0）.Therefore,the application of compound 3 in cell imaging was then explored.The investigation indicates that with the increase of hydrazine,the fluorescence of the red channel decreases significantly,and the fluorescence of the green channel increases.In addition,in terms of mechanism verification,we rarely used the nuclear magnetic resonance,mass spectrometry and crystal structure characterization of the reaction product of compound 3 and hydrazine to directly prove the recognition mechanism.In the presence of hydrazine,levulinic acid first undergoes deprotection.It is removed,and then a dihydropyrazole ring is formed through addition and continuous cyclization reaction.In the hydroxycoumarin system,based on the formation of dihydropyrazole addition cyclization mechanism,four hydrazine fluorescent probes with the structure of hydroxycoumarin chalcone as the sensing site were constructed.Probes 4 and 7 can realize the colorimetric and ratiometric recognition of hydrazine,and have good sensitivity,selectivity and anti-interference.Compared with compound 3,these four compounds have undergone a certain extension of the conjugated chain.Therefore,before and after recognition,the fluorescence blue shifts of probes 4 and 7 reach 188 nm（probe 7）and 229,respectively.nm（probe 4）.Studies have shown that strengthening the positivity of the carbon-carbon double bond and high phenolic activity are conducive to recognition.In terms of application,both of these probes can successfully detect vapor hydrazine within 10 minutes,which can realize portable detection of hydrazine vapor.And the probes also successfully realized the detection of hydrazine in actual water samples.In addition,probe 7 can be successfully applied with cell imaging.Based on the excellent luminescence properties of pyrene,pyrene chalcone derivative compound 8 was synthesized,which can also be used as a naked-eye probe of hydrazine,and still successfully achieved the ratiometric recognition to hydrazine.The detection limit is as low as 1.6 n M（0.053 ppb）,with good sensitivity,selectivity and anti-interference.Compared with the compounds in the previous two systems,the probe has a fast response time with reaction being complete in about 900 s,and the kinetic constant being 2.7×10^-3s^-1.In addition,in terms of application,compound 8 successfully realized the detection of hydrazine in water samples.