Synthesis,Spectral Properties And Application Of Benzothiazole-based Long-wavelength Emission Fluorescent Probes

2-（2′-hydroxyphenyl）benzothiazole（HBT）is a fluorophore with excited-state intramolecular proton transfer（ESIPT）properties.Because of its good fluorescent properties,easy access to raw materials,and simple synthesis,it is widely used in the development of various fluorescent probes.Based on the structural framework of HBT,this paper designed and synthesized four kinds of fluorescent probes through appropriate structural modification,and studied their spectral properties and application potential in detail.1.The fluorescent probe HBTP was designed and synthesized.The probe has a very sensitive response to viscosity.In a methanol/glycerin system,the fluorescence intensity of the probe increases with increasing solution viscosity.According to the fitting results of the F?rster-Hoffmann equation,the probe fluorescence(log I₅₈₃)and viscosity（logη）show a good linear relationship in the range of 13.8 cp to 221.5 cp,so the viscosity can be quantitatively analyzed.In addition,the probe also has excellent photo-stability,outstanding anti-interference ability and good mitochondrial targeting ability,and has been successfully applied to the detection of viscosity changes in biological cells,organs and mice under drug stimulation.2.The fluorescent probe HBTD-P was designed and synthesized.In THF/H₂O（4:6,v/v,PBS 20 mM,pH=7.4）system,the probe has near-infrared emission（683 nm）,and has good selectivity and sensitivity to Pd⁰.The detection limit is 1.26×10^-66 M.The probe can effectively detect Pd⁰ in the concentration range of 0²0μM and the pH range of 7⁹.The test strip made by HBTD-P can effectively detect Pd⁰ in actual environment.3.The fluorescent probe HBTD-M was designed and synthesized.In MeCN/H₂O（1/1,v/v,HEPES 10 mM,pH=7.4）solution,the probe has near-infrared emission（680 nm）and large Stokes shift（240 nm）.The detection selectivity is good,the sensitivity is high,and the applicable pH range is wide（7¹1）.It is successfully used for the detection of Hg²⁺in cells and actual water samples,soil and seafood samples.4.The fluorescent probe HBTM-HC was designed and synthesized.In the presence of masking agent acetone or Fe²⁺,the probe can effectively detect N₂H₄and CN^-in DMSO/H₂O（3/7,v/v,PBS 10 mM,pH=9.1）solution.The probe also has long emission wavelength（620 nm）,large Stokes shift（122 nm）,wide pH range（8-11）,and low cytotoxicity.It can be used for fluorescence imaging of N₂H₄ in biological cells.In addition,the probe can be used to detect CN^-and N₂H₄ in water samples and CN^-in germinated potatoes and apple seeds.