Study On The Synthesis And Application Of Seven-membered Fluoroboron Fluorescent Dyes

For the Fluorine-Boron complexed dipyrromeole(BODIPY)compounds with six-membered ring as the core,they have been extensively studied due to their advantages such as high fluorescence quantum yield,large molar extinction coefficient,simple synthesis steps,easy structure modification,and insensitivity to environmental changes.However,BODIPY dyes still have shortcomings: Stokes shift is small,fluorescence is easily quenched in solid state,etc.For the seven-membered fluorine boron fluorescent dye(BOPYIN)due to the increased degree of conjugation,the resulting compound has better photophysical and chemical properties,such as greater Stokes shift and non-planar configuration(saddle shape).In this paper,a series of seven-membered fluoroboron fluorescent dyes were synthesized by simple method,and by modifying the structure,the spectrum and structural properties were studied to obtain the following results:Four seven-membered BOPYIN ligands with dual effects of AIE and ESIPT were designed and synthesized.The four compounds show significant AIE phenomenon in acetonitrile/water,DMSO/water and THF/water.Their fluorescence intensity is enhanced by 2.8-11.1 times.It is caused by the steric hindrance and hydrogen bond in molecule structure,which further indicate the ESIPT effect and has a large Stokes shift(140 nm).Since the compounds have AIE and ESIPT effects,they are expected to be used in fluorescence imaging and fluorescence probes.A new type of BOPYIN derivative was designed and synthesized,which can be used as a "turn-on" p H fluorescent probe.It has the characteristics of good selectivity,high sensitivity,good stability,short response time and low cytotoxicity,and is suitable for strong acid environment.As the test solution becomes more acidic,the compound's photo-induced electron transfer(PET)process is blocked and the fluorescence is enhanced.A p H value of 3.0-5.5 results in a linear response curve with a p Ka value of 3.63.Because the compound is sensitive to acidity and less cytotoxic,it is used in cell imaging and test strips.A series of BOPYIN derivatives have been designed and synthesized through the benzo indole and ethoxycarbonyl-modified pyrrole.It can be seen from the ultraviolet-visible absorption and fluorescence spectra of the compound that the ?-conjugated structure on the proton acceptor unit of the compound has an ESIPT process.Calculations based on UV-Vis absorption,fluorescence spectroscopy and density functional theory(DFT)proved that the conjugation on the proton acceptor unit and the electron-withdrawing group on the proton donor unit promoted the ESIPT process.Therefore,the ESIPT process can be adjusted through structural modification.A simple two-step one-pot method was used to synthesize a seven-membered fluoroboron compound modified with pyrrole and indole.These compounds have excellent spectral performance and large Stokes shift.The compound BOPYIN-4 has a specific AIE effect.The compound BOPYIN-1-5 has low cytotoxicity and can be applied to biosensors and bioimaging.