Novel Aie Luminogens：synthesis,Property Modulation,Applications In OLED And Lipid Droplet Imaging

Due to the rigid molecular structure of traditional fluorescent dyes,strongπ-πinteractions in the solid state or in the aggregated state can cause fluorescence quenching.However,the aggregation-induced emission（AIE）material has the opposite luminescence behavior in the solid state.Therefore,the unique photophysical phenomena of AIE materials can be applied in various fields,such as the organic light-emitting diodes,fluorescence sensing,bioimaging and explosive detection so on.This thesis focuses on the concept of AIE to design and synthesize noval AIE luminogens.By realizing the relationship between molecular structure and properties,we have got the luminogens with high emissive property and exhibit the excellent performances in OLED and bioimaging.In chapter 2,we designed and synthesized novel blue luminogens with AIE active containing an anthracene core and various functional groups.The thermal stabilities,photophysical properties,electronic structures,electrochemical behaviors,carrier transport abilities and electroluminescence performances are systematically investigated.The luminogen TPE-TAPBI containing a tetraphenylethene moiety shows aggregation-induced emission（AIE）characteristic,while the other luminogen TriPE-TAPBI bearing a triphenylethene unit exhibits light aggregation-caused quenching effect.In comparison with TriPE-TAPBI,TPE-TAPBI has stronger blue emission in solid film and functions more efficiently in nondoped OLEDs.High maxima current,power and external quantum efficiencies of 7.21 cd A^-1,6.78 lm W^-1 and 5.73%,respectively,are attained by the nondoped blue OLED of TPE-TAPBI(CIE_x,y=0.15,0.16).In addition,efficient two-color hybrid warm white OLEDs(CIE_x,y=0.45,0.46)are achieved using TPE-TAPBI neat film as the blue-emitting component with low roll-off efficiency,which provide total current,power,external quantum efficiencies of up to 70.5 lm W^-1,76.0 cd A^-1 and 28%at 1000 cd m^-2,respectively.In chapter 3,a series of new red fluorescent siloles consisting of a silole core and dimesitylboranyl substituent connected with a furan,thiophene,and selenophene bridges were synthesized and characterized.The optical properties,electronic structures,and electroluminescence（EL）performances were investigated.The emission wavelengths were red-shifted from the siloles with furan,to those with thiophene,and then selenophene.The thiophene,and selenophene-containing siloles,（MesB）₂DTTPS and（MesB）₂DSTPS,showed the typical aggregation-enhanced emission（AEE）feature,while furan-containing one,（MesB）₂DFTPS,showed slight emission decrease as the aggregate formation.Theoretical calculations were carried out to explain the difference in the optical properties.Undoped OLEDs using these red siloles as light-emitting layers were fabricated.The device of（MesB）₂DTTPS exhibited the best performance.It radiated red EL emission at 589 nm,and afforded good maximum luminance,current,power,and external quantum efficiency of13300 cd m^-2,4.3 cd A^-1,2.9 lm W^-1 and 1.8%,respectively.In chapter 4,the boron atom as the main group was directly connected with the silole ring to design and synthesize three novel kinds of 2,5-bis（dimethylboryl）-3,4-diphenylsiloles.The electron can delocalize between the p orbital and the silole ring.Thus,the absorption and emission wavelength are red-shifted than that the silicon atom attacthed.The spatially crowded molecular structure reduces the rate of change of the molecular configuration,which results in the appearance of a broad NMR spectrum of small molecules at room temperature.The single crystal structure confirms that there is a large number of C-H···πinteractions in this molecule.The reduction of the intramolecular configuration does not change the AIE properties.Electrochemical experimental results show that the new boron-containing silole has a low LUMO energy level,which can be used as an electron transport layer in OLED devices.In chapter 5,we report that a series of novel propeller-like luminogens consisting of a thieno[3,2-b]thiophene S,S-dioxide core and different phenyl rotors can behave oppositely.They show faint emission in solutions,but can fluoresce strongly in solid films,displaying prominent AIEnature.Crystallographic,computational and spectroscopical results reveal the synergistic effect of a propeller-like conformation and the oxidation of thieno[3,2-b]thiophene to thieno[3,2-b]thiophene S,S-dioxide greatly enhances emission efficiency of the luminogen in solid film.The theoretical calculation and electrochemistry reveal that the LUMO energy of TTDO system is lower than oxidation before.What’s more,they as acceptor can be built D-A structure luminogens with strong electron affinity.This work not only presents a feasible approach to create robust luminescent materials from thipohene but also provides a new AIE platform with advantages of structural variety,high solid-state emission efficiency and strong electron affinity so on.In chapter 6,we report the synthesis and characterization of a series of novel dipolar luminogens based on thieno[3,2-b]thiophene S,S-dioxide（TTDO）.The crystal strucutres,photophysical property,thermal stability,electronic strucutres and electronchemical behaviors of these TTDO-based luminogens are investigated.These luminogens have good AIE property with high solid-state fluorescence quantum yields,and their emission wavelengths are tuned from green to red by different electron-donating substituents.They enjoy high thermal and morphological stability,and have low LUMO energy levels.Nondoped OLEDs are fabricated with these new luminogens,providing orange to red electroluminescence（568?610 nm）with maximum external quantum efficiencies of up to 2.79%.These results demonstrate that these new AIE-active luminogens could be promising candidates for OLEDs.In chapter7,a polar sensitive lipid droplet probe with AIE fetures was developed for the movement and metabolism tracing of lipid droplet by monitoring the fluorescent signal changes.TPA-BTTDO nonaparticles（TPA-BTTDO NPs）with well biocompatibility was prepared based on co-precipitation method.TPA-BTTDO NPs can cross the cell membrane via endocytosis process,and prefer to locate in lipid droplet compared to lysosome.What’s more,two different fluorescence signals were detected after incuation with HeLa cells,red fluorescence in lysosome and blue fluorescence in lipid droplet,which shows polar sensitivity.By monitoring the fluorescent signal of NPs,the quick movement of lipid droplet could be visualized with high sensitivity.Besides,we figured out that TPA-BTTDO NPs located in lysosome at first,and escaped from losome after internalization for 4 h followed with the reterun back to lysosome at last with blue emission via monitoring the changes in colour of fluorescent signal.This polar sensitive probe holds a great promise in studying the formation and functions of lipid droplet even the diagnosing the diseases related to lipid droplet.