Design And Synthesis Of Novel Single Benzene And Near-infrared ? Molecular Dyes For Imaging

Fluorescent imaging analysis methods based on fluorescent dyes,due to their high sensitivity,good selectivity and rapid response,have shown more and more in environmental monitoring,biological imaging,food safety and life sciences.The electron donor-acceptor(D-A)type small molecule dyes and cyanine dyes are widely used in the design of fluorescent imaging probes due to their excellent photophysical properties,simple structure and easy modification.However,most D-A small molecule dyes and cyanine dyes have problems of environmental sensitivity,small Stokes shift,poor photostability,and easy fluorescence quenching in water environments.These problems make the brightness of the biological imaging week,resulting in low sensitivity of probe detection,which limits its further application in living systems.In order to meet the needs of biological analysis and imaging research,it is very necessary to develop new D-A small molecule dyes and cyanine dyes with better performance.In response to the above problems,this article carried out the following work:Firstly,we designed and synthesized a new class of D-A small molecule fluorescent dye(SB-Flour)with a single benzene skeleton for the problems of traditional D-A organic fluorescent dyes that are easily quenched under high concentration or aggregation state,sensitive to the environment,difficult to accurately adjust the wavelength,and quenched in aqueous solution.Compared with traditional D-A dyes,SB-Flour dyes are simple in structure,have a smaller conjugated system,and have only one benzene.This small skeleton structure not only makes SB-Flour have good solubility,but also makes it show solvent insensitivity and good solid-state light-emitting performance.In addition,due to the strong intra-and intermolecular charge transfer,the SB-Flour dye exhibits a high fluorescence quantum yield and a large Stokes shift,which is very conducive to the development of high-signal-to-back ratio and high-sensitivity fluorescent probe.By changing the electron-donating ability of the electron donor,the wavelength of the single benzene structure dye can be precisely adjusted,and its wavelength can extend from the ultraviolet visible region to the near infrared region.In addition,through the grinding of solid powder,we found that SB-Flour dye has very good reversible mechanical luminescence property.Stability studies and two-photon test experiments show that SB-Flour dyes also have excellent photostability and solid-state two-photon luminescence properties,and have great potential for application in two-photon imaging.Secondly,in response to the problems of small Stokes shifts and poor photostability of the current cyanine NIR-II dye,we have developed a large Stokes-shifted NIR-II fluorescent dyes DQF-910 and DQF-941 by introducing 1,4-diethyl decahydroquinoxaline structure into cyanine dyes.The introduction of the quinoxaline structure of the strong electron-donating group breaks the symmetrical electronic structure of traditional cyanine fluorescent dyes,so that the wavelength is extremely red-shifted and reaches the near-infrared region.At the same time,the asymmetric electronic structure also makes the Stokes shift significantly increased(69 nm),much higher than the traditional cyanine NIR-II dyes(generally <30 nm).Stability and solvation test research show that the compounds DQF-910 and DQF-941 have high chemical stability and light stability,and can effectively resist the solvated fluorescence quenching effect.In addition,in order to enhance the water solubility of this type of dye,we introduced galactose into the molecular structure of the dye and synthesized the compound DQF-910-Gal,which effectively improved the water solubility of this type of dye.These results indicate that the new Cy dye will have a very good prospect for bioimaging applications.