Design,synthesis And Application Of Fluorescent Probes Of Hemicyanine Dyes Baesd On Benzothiazole

Fluorescence analysis technology is widely used in environmental testing and life medical due to its simple operation,high sensitivity and low detection limit.Fluorescence probes can not only detect neutral small molecules and metal ions,but also perform sequencing and calibration of biomolecules such as nucleic acids and proteins.Besides,the detection of environmental sensitive factors,including polarity,viscosity and pH,is particularly concerned by researchers.Cyanine dyes are widely used in bioanalysis due to their excellent photophysical properties,outstanding biocompatibility,and low toxicity to living systems.In this work,aiming at the detection of environmental sensitive factors,four cyanine dyes were designed and synthesized for viscosity and pH detection,respectively.The structure of the compounds was characterized by 1H NMR,13 C NMR and HRMS.The photophysical properties of the molecules were determined by UV-vis and fluorescence spectroscopy.The specific research contents as follows:(1)Based on the mechanism of intramolecular charge transfer,two novel styrylcyanine dyes,DPA-1 and DPA-2,composed of an electron-rich N-phenylaniline and a cationic benzothiazene connected with ethylene(s)bridge,were designed and synthesized.These two dyes exhibited red-emission(653/607 nm)and simultaneously impressive large Stokes shift(111/92 nm)due to intramolecular charge transfer effect,twisted geometry and extended conjugation system.When their solution viscosity increased from 1.01 cP to 234 cP in the water-glycerol system,the fluorescence intensity of the synthetic dyes was enhanced by 81-fold and 64-fold,respectively.Additionally,a favorable linear relationship between the fluorescence intensity and the environmental viscosity was observed within the above viscosity range for the obtained samples(R2 > 0.99),which led to the establishment of a method for the quantitative determination of the solution viscosity.Moreover,the mechanism of fluorescence emission of the resultant products toward viscosity was further investigated by low temperature spectrum and the solid state fluorescence spectrum.Such dyes with improved photophysical properties,including emission wavelength and Stokes shift,could be used as promising candidates for intracellular viscosity detection.(2)Two hemicyinine dyes,BTZ-1 and BTZ-2,composed of a cationic benzothiazene and naphthalene ring carrying different substituents with ethylene bridge,were designed and successfully synthesized.These two samples exhibited orange-emission(589/571 nm)and simultaneously impressive large Stokes shift(157/144 nm)respectively.The pH titration results showed that their absorption/emission spectra underwent a shift with the variation of pH of the solution.Moreover,a significant color change of the solution could be observed by the naked eye,which facilitated visual observation.Spectral testing eliminated interference of the polarity,viscosity and metal ion,which indicated that the probes could be used as promising candidates for determining intracellular pH.