Design,Synthesis And Application Of Novel Near-Infrared Fluorescent Dyes

With the advantages of high sensitivity,good selectivity,and simple operation,fluorescence imaging technology has developed rapidly in recent years.Fluorescence imaging technology has become a powerful tool for detecting various active species in life activities and changes in microenvironmental parameters.Fluorescence imaging technology is inseparable from fluorescent probes and luminescent dyes used to construct fluorescent probes.At present,the absorption and emission wavelengths of many fluorescent dyes are located in the visible light region,which have problems such as large background interference,weak biological tissue penetration,and photobleaching,which limits its application in biological detection to a certain extent.In contrast,near-infrared(NIR)fluorescent dyes have great advantages in biological detection,such as low background interference,strong penetration ability,and little light damage,which have broad application prospects in cell and tissue imaging.Therefore,the design and synthesis of new NIR fluorescent dye is the focus of current research.In this paper,based on the research status of near infrared fluorescent dyes in recent years,four kinds of NIR fluorescent dyes were successfully constructed and their photophysical properties were explored,which could be divided into the following three parts:1.The NIR fluorescent dye 1 was constructed by linking the benzomerocyanine structure and the malononitrile structure to form a large π-conjugated skeleton.The NIR fluorescent dye1 had a good viscosity response,in the high viscosity environment,the rotation of the molecular rotor malononitrile and the rotation of single double bond in the large π-conjugated structure in dye 1 was inhibited,the energy loss was reduced,the fluorescence of dye 1 was enhanced.In order to further study the relationship between viscosity response and rotation sites,the morpholine group was attached to the basis of NIR fluorescent dye 1,and the NIR fluorescent dye 2 was designed and constructed.The existence of morpholine group made the dye 2 had more rotation sites.When the viscosity was changed from 0.6 cp to 657.4 cp,the fluorescence of dye 1 was enhanced about 7.2-fold and the fluorescence of dye 2 enhanced about 8.4-fold.This indicated that the increase in rotation sites made the dye molecules more sensitive to the viscosity response,and dye 2 had a higher fluorescence quantum yield and a larger Stokes shift than dye 1 under the same conditions.Both dyes 1 and 2 had good photostability and p H stability,and had good selectivity for viscosity,which could be used for quantitative measurement of viscosity.2.A NIR fluorescent dye 3 with viscosity response was designed and synthesized by conjugation of dimethylaminobenzaldehyde and the onium salt based on the oxanthene structure.The viscosity response of dye 3 was achieved by limiting the rotation of dimethylaniline and single double bonds.Dye 3 showed weak fluorescence in low viscosity environments and strong fluorescence in high viscosity environments.In addition,dye 3 showed good selectivity,p H stability and photostability,which enabled the quantitative determination of viscosity.Dye 3 was successfully applied to the determination of bovine albumin(BSA)content in water.3.By linking the benzomerocyanine structure,the isophorone structure and malononitrile structure,we reported a NIR fluorescent dye 4 with large Stokes shift.The photophysical properties of dye 4 had been studied,and experimental datas showed that dye 4 had a large Stokes shift,good photostability and p H stability.