Synthesis And Recognition Performance Analysis Of Symmetric Cyanine Based On Thiophene And Bithiophene Ligands

The imbalance of sulfur dioxide concentration in living organisms is closely related to the physiological process of some diseases,such as enhanced cellular antioxidant capacity,molecular signal transduction and so on.Endogenous sulfur dioxide is generated by enzymatic metabolism of mercaptan compounds in living organisms.Take cyanine dye as model,thiophene or bithiophene structure was introduced as the electron-donating linking group of the dye molecule,which combined with the strong electron-absorbing group to form the fluorescent molecular structure with intramolecular charge transfer（ICT）luminescence mechanism.Further study on its recognition performance for the detection of sulfur dioxide at the cellular level.This paper mainly carries out the following work:（1）By introducing the strong electron-absorbing group（benzothiazole or quinoline group）and connecting with methylene groups to form a largeπconjugated system,the double responsive probes TEO and TEQ were constructed.The two ratio fluorescent probes can react with HSO₃^-/SO₃^2-in water system with Michael addition reaction,and the conjugate system is destroyed,and the UV absorption and fluorescence emission spectra change obviously.Their detection limits are less than 80n M and the response time is more than 10 min.At the same time,the two probes can detect the viscosity of solvent sensitively,and the fluorescence lifetime of probe TEO is longer than that of probe TEQ.Due to their low cytotoxicity,the two probes were successfully used to detect extracellular/endogenous sulfur dioxide derivatives and viscosity of He La cell.（2）Thiophene groups are covalently bonded with benzothiazole or benzoindole groups to obtain probes DTEO or DTEI,which produce obvious push-pull electron effect and have a reaction-type spectral response to HSO₃^-/SO₃^2-,and have higher sensitivity and selectivity than the aforementioned probes TEO and TEQ（DTEI has a response time of less than 20 s and detection limit of less than 0.7 n M）.Cell imaging experiments demonstrated that probes DTEO and DTEI could detect extracellular/endogenous sulfur dioxide derivatives.In addition,the two probes have their own advantages.The Stokes shift of the probe DTEO reaches 105.5 nm,and DTEO can be targeted to the nucleus（Pearson coefficient is 0.97）.The maximum emission wavelength of DTEI reaches 666 nm,and it is also capable of detecting HSO₃^-/SO₃^2-two-channel ratio in living cells.