Synthesis And Application Of Benzothiazole-based Fluorescent Probes

In recent years,benzothiazole derivatives have been widely used in medicine,pesticides,materials,dyes,and other fields.Among them,benzothiazole Schiff base compounds have p-πandπ-πconjugated systems,structural units such as-C=N-,-OH,-S-,which could combine with metal ions to produce fluorescence effects.Therefore,benzothiazole derivatives can be used as fluorescence probes for metal ion detection.In this thesis,three benzothiazole Schiff base fluorescent probes have been designed and synthesized in order to achieve immediately,specificity,and naked detection of silver or zinc ions.The main specific research contents of this paper are as follows:1.Benzothiazole-2-formyl hydrazide was prepared by the reaction of benzothiazol-2-carboxylic acid ethyl ester with hydrazine hydrate,then which condensed with 4-diethylaminosalicylaldehyde to obtain fluorescence probe L1with a yield of 68.4%.The probe could quickly identify zinc ions to form 1:1complexes in DMSO solution and exhibit significant fluorescence enhancement effects,which could achieve"turn-on"detection of zinc ions with the advantages of good selectivity and strong anti-interference.With the concentration range from 0 to 5μM,there was a good linear relationship between fluorescence intensity and zinc ion concentration,and the LOD was calculated to be 15.8 n M.The probe was used for the detection of zinc ions in soil,the experimental recovery rate was 95.72～103.2%,relative standard deviation was 1.79～5.92%,which presented good practical application capabilities.2.2-hydrazinobenzothiazole was prepared by the reaction of2-mercaptobenzothiazole with hydrazine hydrate,then which condensed with5-phenyl-2-thiophenecarboxaldehyde to obtain fluorescence probe L2 with a yield of 74.6%.The probe could quickly form a 1:1 complex with silver ions in THF/HEPES（4/6,v/v,p H=7.4）solution,and realize the"on-off"detection of silver ions with the advantages of good selectivity,low detection limit,and strong anti-interference.With the concentration range from 0 to 10μM,there was a good linear relationship between fluorescence intensity and silver ion concentration,and the LOD was calculated to be 72.0 n M,which could achieve trace detection of silver ion.The probe was used to detect silver ions in actual water samples with excellent results,the experimental recovery was 86.29%～107.1%and relative standard deviation was 1.78%～4.59%.3.The fluorescence probe L3 was obtained by condensation reaction between 2-hydrazinobenzothiazole and benzothiophene-2-formaldehyde with a yield of 80.9%.The probe could quickly identify zinc ions to form 1:1 complexes in DMSO solution and exhibit significant fluorescence enhancement effects to achieve"turn-on"detection of zinc ions.With the concentration range from 0 to11μM,there was a good linear relationship between fluorescence intensity and zinc ion concentration,the probe had a high sensitivity for recognition of zinc ions with a detection limit of 19.1 n M.The probe was used to detect zinc ions in actual water samples,the experimental recovery was 96.15%～103.37%,and the relative standard deviation was 0.98%～4.15%.Meantime,the complex between probe and zinc ion L3-Zn²⁺could achieve a specific"on-off"detection of glyphosate with a detection limit as low as 16.0 n M and strong anti-interference.The complex L3-Zn²⁺also was used for the detection of glyphosate in water with excellent experimental results,the experimental recovery rate was91.91%～102.65%and the relative standard deviation was 1.81%～5.92%.The probes and intermediate compounds synthesized in this paper were characterized by ¹H NMR,¹³C NMR,IR and HRMS.