Synthesis And Characterization Of Fluorescent Probes Containing Tetraphenylethylene Units With Metal Ions Response

Metal ions are widely present in the natural environment and affect the life activities of organisms,especially heavy metal ions.Excessive or slight intake of heavy metal ions will affect some organs of the human body,thereby increasing the probability of suffering from a series of diseases.Based on the advantages of fluorescent probes such as high sensitivity,high selectivity and fast response,in recent years,fluorescent probes have been widely used in the detection of metal ions.In this paper,four metal ion probes,Probe 1,Probe 2,Probe 3 and Probe 4 were synthesized.Probe 1 was a Hg²⁺enhanced fluorescent probe,Probe 2 and Probe 3 were Cu²⁺quenched fluorescent probes,and Probe 4 was a Cu²⁺enhanced probe.The main research contents and results of this paper were as follows:1.Compound 2-（2-（2-aminophenoxy）ethoxy）aniline（QH-NH₂）was synthesized by substitution reaction using ortho-hydroxyphenol and 1,2-dibromide as raw materials.Compound 1,1,2-triphenyl-2-（4-formaldehyde benzene）ethylene（TPE-CHO）was synthesized from triphenyl bromide ethylene and 4-formylphenylboronic acid by Suzuki coupling reaction.Compound Probe 1 was synthesized by Maillard reaction using QH-NH₂and TPE-CHO.The chemical structures and optical properties of Probe 1 was characterized by NMR,FTIR and LC-MS,et al.The optical properties of Probe 1 tested by UV-Vis and PL.The conclusions were as follows:in the THF/H₂O mixed solvents,when the water fraction increased from 0%to 30%,the fluorescence intensity had dropped significantly;when the water fraction increased from 30%to 50%,the fluorescence intensity increased;when the water fraction increased from 50%to 99%,the fluorescence intensity gradually decreased,and the maximum emission wavelength was red-shifted.In summary,when the water fraction was 30%-50%,the AIE effect of Probe 1 was obvious.Using Probe 1 as a fluorescent probe to detect Hg²⁺,the results were as follows:in the THF/H₂O（50/50,V/V）mixed solvents,Probe 1 complexed with Hg²⁺which resulted in fluorescence enhancement.Other metal ions had no interference to the responsiveness of Probe 1 to Hg²⁺,and the detection limit of Probe1 was 0.25μM.The possible coordination model for Probe 1 and Hg²⁺was given.2.Compound 1-（4-（1,2,2-triphenylvinyl）benzylidene）hydrazine（M1）was synthesized by using TPE-CHO and hydrazine hydrate as raw materials.Compound8-formyl-7-hydroxy-4-methylcoumarin（M2）wassynthesizedfrom7-hydroxy-4-methylcoumarin and 4-aminobenzophenone by Duff reaction.Compound Probe2 was synthesized by Maillard reaction using M1 and M2.Synthesis of Probe 3:Firstly,carbazole was nitrated to generate 2-nitrocarbazole（M3）,then M3 was reduced to2-aminocarbazole（M4）,and finally,M4 and M2 subjected to Maillard reaction to synthesize the compound Probe 3.The test results of Probe 2 showed that:in the DMF/H₂O mixed solvents,when the water fraction increases from 0%to 20%,the fluorescence intensity of Probe 2 increased and the maximum emission was blue-shifted;the water fraction increased from 20%to 50%,the fluorescence intensity of Probe 2 decreased to a certain extent;when the water fraction increased from 50%to 90%,the fluorescence intensity of Probe 2gradually increased and reached the maximum at 90%,simultaneously,the maximum emission wavelength is red-shifted.In summary,Probe 2 had the AIE effect.The fluorescence of Probe 2 was quenched after adding Cu²⁺,and no interference from the other metal ions.The lower detection limit was 0.45μM.The test results of Probe 3 showed that Cu²⁺can interact with Probe 3 to cause its fluorescence to be quenched without interference from other ions,and its detection limit was 0.11μM.3.The compound methyl 4-（1,2,2-triphenylvinyl）benzoate（M5）was synthesized by Suzuki coupling reaction using triphenyl bromide ethylene and4-methoxycarbonylphenylboronic acid as raw materials;then M5 was hydrolyzed to generate1,2,2-Triphenyl-1-（4’-carboxyphenyl）ethylene（M6）;finally compound Probe 4 was synthesized by condensation reaction with M6 and 8-aminoquinoline.The test on Probe 4found that it had AIE（Aggregation-induced Emission）effects.The optical properties of Probe 4,and the fluorescence was enhanced with Cu²⁺in the CH₃CN/H₂O（10/90,V/V）mixed solvents,simultaneously,the Cu²⁺response of Probe 4 had no interference from the other metal ions.The test of Cu²⁺response of Probe 4 also indicated that it had lower detection limit with 0.15μM.This thesis successfully synthesized four metal fluorescent probes,Probe 1,Probe 2,Probe 3 and Probe 4.Probe 1 had good selectivity and high sensitivity to Hg²⁺,and can be used as a fluorescent probe to detect Hg²⁺.Probe 2,Probe 3 and Probe 4 were responsive to Cu²⁺,providing ideas for the design and synthesis of Cu²⁺fluorescent probes.