Design,Synthesis And Application Of New Near-Infrared Fluorescent Probes Based On β-Diketone Boron Difluoride

Fluorescence imaging technology has become an important research tool in the fields of chemistry,biology and medicine due to its advantages of high sensitivity,good selectivity and spatio-temporal resolution,non-invasive visualization and real-time operation.The development of fluorescence imaging technology cannot be separated from excellent fluorescence probes.Especially,the near-infrared fluorescence probes have the advantages of deep penetration,little light damage and low background interference,and are widely used in fluorescence imaging technology.Common dye molecules used to construct fluorescent probes include fluorescein,coumarin,Rhodamine,cyanine and BODIPY.The near-infrared fluorescent probes constructed with β-dione boron difluoride as structural units have the characteristics of high molar extinction coefficient,high fluorescence quantum yield and easy synthesis.So near-infrared fluorescent probes based on β-dione boron difluoride have received more and more attention.In this paper,we introduce different substituents through multi-component reactions,designed to increase the length of conjugate chains,introduced conjugate groups,and designed and synthesized four kinds of near-infrared fluorescence probes based on β-dione boron difluoride structural units.The optical tests show that these near-infrared fluorescence probes have the advantages of high fluorescence quantum yield,high molar absorption coefficient,long absorption and emission wavelength,and large Stokes shift.In addition,these probes have significant solvation phenomenon in solvents of different polarity and are sensitive to polarity,which are expected to provide a good fluorescent probe tool for near infrared polarity detection.The main research contents of this paper include:1.A novel near infrared fluorescence probe CO-DBD based on β-dione boron difluoride was designed and synthesized.Probe CO-DBD had a "donor-acceptor-donor" skeleton structure,and will undergo intramolecular charge transfer(ICT)and twisted intramolecular charge transfer(TICT),exhibit polarity sensitivity,high fluorescence intensity and short emission wavelength in low polar solvents.The photophysical properties of the probe CO-DBD were tested in detail,and it was found that the probe has near infrared emission and good polarity response.In particular,the quantum yield of probe CO-DBD was higher than 0.5 in low polar solvents such as toluene and 1,4-dioxane.The theoretical results showed that the polar response was caused by ICT and TICT processes.In addition,the probe had good polarity selectivity,p H and time stability,and can be used to accurately detect the polarity of binary mixed solvents.Cell imaging experiments showed that the probe CO-DBD had good membrane permeability and could be used for imaging living cells.2.A series of derivatives CO-L1,CO-L2 and CO-L3 were constructed based on β-dione boron difluoride framework,and the effects of substituents and conjugated systems on the fluorescence properties were studied.The experimental results showed that the fluorescence wavelength of β-diketone boron difluoride derivatives varied with the intensity of electron donors at both ends.The higher the electron donor capacity,the longer the fluorescence wavelength of the compounds,and the change of the rigid plane of the compounds resulted in the change of the corresponding dye fluorescence wavelength.It was found that probes CO-L1,CO-L2 and CO-L3 were also based on ICT and TICT processes,and showed higher fluorescence intensity and shorter emission wavelength in low polarity solvents.Optical tests showed that the probe has the advantages of large Stokes shift,high fluorescence quantum yield,excellent selectivity and stability.By using probes CO-L1,CO-L2 and CO-L3,we successfully realized the accurate detection of polarity parameters of binary mixed system.