Design,Synthesis And Imaging Applications Of Organic Red And Near Infrared Fluorescent Materails With High Performance

Fluorescence imaging technology exhibits several advantages,including low cost,ease of operation,high sensitivity and friendliness to biological samples,which has been extensively utilized in the fields of biomedical and materials science.Considering that organic red and near infrared(NIR)fluorescent materials possess the merits of good biocompatibility,little interference from auto-fluorescence and deep tissue penetration,fluorophores with red and NIR emission are especially preferable in high resolution imaging.Therefore,it has not only scientific significance but also practical application value to develop high performance organic red and NIR fluorescent materials to reveal the relationship between molecular structure and function.This paper mainly focuses on the design and synthesis of organic red and NIR fluorescent materials as well as their optical imaging properties.The main contents are as follows:1.The polarity-activated red emission probe(E)-1-butyl-4-(2-(5-(9-ethyl-9H-carbazol-2-yl)thiophene-2-yl)vinyl)pyridiniu bromide(CTPB)is designed and synthesized.The hydrophilic pyridinium bromide group is introduced as electron acceptor and the lipophilic carbazole together with the thiophen bridge groups serves as an extended donor.Note that CTPB in aqueous solution remain weakly emissive and the obvious enhancement in emission intensity is observed when matured insulin amyloid fibrils are added.With the merits of large Stokes’ shift,high binding affinity,excellent photo-stability and high brightness,the process of insulin aggregation in vitro with nanoscale resolution is visualized by super resolution microscopy.This study paves a novel way for understanding the formation and morphology of amyloid fibrils.2.Bromofumaronitrile(BFO)is selected as novel building block to design and synthesize aggregation induced emission(AIE)probes 2,3-bis(4-(4-methylpiperazin-1-yl)phenyl)fumaronitrile(PIZ-CN)and(E)-4,4’(1,1’-(4,4’-(1,2-dicyanoethenebis(4,1-phenylene)bis(piperidine-4,1-diyl)(PID-CN)through simple targeting groups modification,which show specific lysosomes and mitochondria targeting capability,respectively.The results demonstrate that the loosely molecular packing can avoid π-πinteractions effectively and the short interactions can suppress molecular motions to realize AIE effect.In contrast with commercial lysotracker and mitotracker,all the results confirme that PIZ-CN and PID-CN can achieve high fidelity imaging with higher photo-stability and larger Stokes’ shift.Furthermore,it is observed the dynamic motions of lysosomes and mitochondria in living cells with high nanoscale resolution,which warrant great potentials for their real applications.3.Two NIR fluorophores(Z)-3-(7-(9-ethyl-9H-carbazol-3-yl)benzo[c] [1,2,5]thiadiazol-4-yl)-2-(4-(pyridin-4-yl)phenyl)acrylonitrile(CASN)and(Z)-3-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)-2-(4-(pyridin-4-yl)phenyl)acr ylonitrile(TASN)are successfully synthesized with high solid state emission.The emission wavelength can be easily tuned by altering the electron donor to trigger more efficient charge transfer transition to ensure large Stokes’ shift.By optimizing electron donors and introducing steric groups,the molecular stacking is effectively regulated and intermolecular interactions is reduced as well.TASN powders are chosen to combine with nontoxic and high absorptive capacity of montmorillonite(MMT)as a new composite for developing LFP based on powder dusting method.It will also inspire more insights into the development of high performance fluorophores to extend the usefulness of powder dusting method.4.A novel luminogen(Z)-2-(4’-(diphenylamino)biphenyl-4-yl)-3-(7-(9-ethyl-9H-carbazol-3-yl)benzo[c][1,2,5]thiadiazol-4-yl)acrylonitrile(DBCT)is developed through regulating molecular packing modes and intermolecular interactions.The solid state emission can be reversibly from bright orange to red with high contrast through pressing(0.6 MPa),heating and solvent fuming.Single crystal X-ray analysis and theoretical calculations verify that the reversible luminescence switching characteristic is highly related to the different molecular packing mode within crystals,which amplifies the exciton coupling effect and results in distinguishable red-shifted emission.The prepared writable fluorescent inks with high contrast and brightness for security anti-counterfeiting applications,which hold great potentials in the field of anti-counterfeiting imaging and information encryption.