Construction Of Deep Blue Luminescent Materials Based On Polycyclic Aromatic Hydrocarbon Compounds And Their Photophysical Properties

Organic Light-Emitting Diode(OLED)displays are a competitive alternative to Liquid Crystal Displays(LCDs)due to their self-emission,high contrast ratio,full viewing angle,power efficiency and mechanical flexibility.In order to realize the ultra-high-definition display of OLED screens,extremely narrow half-peak widths and high-efficiency monochromatic RGB(Red,Green,Blue)light-emitting materials are essential.Among the three primary colors of RGB,the color purity and luminous efficiency of red light and green light have reached the industry standard,while the comprehensive performance of blue light materials is far from enough.Therefore,developing high-performance blue-light materials is one of the most challenging tasks in the OLED field.This thesis is mainly based on polycyclic aromatic hydrocarbon materials,through molecular design engineering to design and synthesize blue light molecules,and study the special photophysical properties of blue light materials.The main research contents are as follows:(1)A novel anthracene bromide intermediate was developed by brominating the anthracene ring catalyzed by iron powder.Four novel anthracene-based blue light materials were prepared by palladium catalysis.Studies have shown that the photoluminescence spectrum of these compounds is at 438-458 nm,showing pure blue emission and high fluorescence quantum yield(0.46-0.59).Furthermore,through a simple and controllable light-induced domino reaction,stable organic radicals were successfully obtained from2,3,6,7,9,10-hexaaryl-substituted anthracene system.In-depth studies have shown that the electronic effects of substituents can affect the light-induced domino reaction process.When the 2-,3-,6-,7-,9-,and 10-positions of anthracene are substituted by the donor group4-tert-butylphenyl,the The bulk unit can effectively stabilize the superoxanthracene group without further light-induced domino reaction to obtain free radicals.However,when the electron-donating group 4-methoxyphenyl is used at the end,the light-induced domino reaction showed good controllability under ultraviolet light,and stable EPO,semiquinone and semiquinone radicals were obtained,respectively.However,due to the strong electron-withdrawing properties of 4-formylphenyl and 4-trifluoromethyl,the corresponding anthracene derivatives are more prone to photodegradation process,resulting in compounds with ambiguous structures.The entire light-controllable domino reaction process was characterized by NMR spectroscopy,HRMS and X-ray single crystal diffraction.According to theoretical research,a feasible light-induced controllable domino reaction mechanism was proposed.(2)Four new azaarenes blue-light materials were prepared by introducing different substituents at the 2-,3-and 6-,7-positions of the quinoxaline group.With the increase of substituent groups,the thermal stability of the material also increases.The fluorescence spectra show that the four molecules emit dark blue/blue light in both solution and solid state,and the maximum emission peaks in solution state are located at 413 nm,425 nm,416 nm and 417 nm,respectively.The CIE coordinates are(0.16,0.03),which is close to the standard deep blue CIE coordinates(0.14,0.03).The comparative study found that the addition of substituent groups can effectively inhibit the intermolecular interaction and improve the blue light performance of the material.It is worth noting that the atypical AIE performance of compound 1,its fluorescence intensity gradually increases with the increase of water content,and the fluorescence intensity is enhanced by about 10 times when the water content is 80%,while when the water content increases to 90%,due to the increase of water content.The molecules are tightly packed and the ?-? conjugation is enhanced,resulting in a rapid drop in fluorescence intensity.(3)Five carbazole-like blue light molecules with different molecular configurations were constructed to study the influence of molecular configuration and electronic effect on the photophysical properties of the compounds.Compounds 1-5 all have blue emission peaks located at 372 nm to 471 nm.Quantitative calculations show that molecules with central nuclear groups containing N and O atoms have stronger electron-withdrawing ability,deeper LUMO energy levels,and red-shifted emission spectra.Among them,compounds 1and 4 both exhibit selective phosphorescence emission.The difference in phosphorescence emission between crystals and thin films indicates that the phosphorescence emission is related to the way of molecular packing.X-ray single crystal diffraction and X-ray powder diffraction indicate that close crystal packing induces molecular phosphorescence emission.This is an effective means to develop high-performance RTP materials by reducing nonradiative transitions and external quenching.