Synthesis And Property Study Of Organic Delayed Fluorescence And Phosphorescence Materials Based Pyrazines

Organic light-emitting materials have broad application prospects in many fields such as photoelectric functional devices,biomedicine,sensors,and anti-counterfeiting.Aggregationinducing luminescent materials with delayed fluorescence and room-temperature phosphorescence emission characteristics are considered to be effective ways to solve the problem of fluorescence quenching of organic light-emitting materials in organic light-emitting diodes,improve device luminous efficiency,and reduce device cost.In this thesis,a new type of aggregation-induced emission(AIE)luminescent materials with delayed fluorescence and room-temperature phosphorescence emission characteristics were synthesized.The photophysical properties of these compounds were studied.The theoretical and experimental results indicate that AIE activity based on with delayed fluorescence and room temperature phosphorescent characteristic;those results established a foundation for the development of low cost and high efficiency OLED luminescent materials.The main contents are as follows:(1)The condensation reaction between benzils having a different substituent and diaminomaleonitrile to obtain a 5,6-diphenyl-2,3-dicyanopyrazine compound.Enhancement of electrons with substituents,spectrum is gradually red-shifted from blue to red light,which realizes the change of the color of the luminescence.The quantum efficiency of the compound 1 in the solution is relatively low,but the crystal state is as high as 70.47%,showing AIE activity;Their steady-state and transient spectra were studied and found that those compounds with delayed fluorescence and phosphorescence emission characteristics at room temperature.In particular,the luminescence color of compound 2 in low-temperature toluene solution was close to pure white light,and the CIE coordinates were(0.30,0.37);This provides a new research idea for the study of full color control and white light emission.(2)Luminescent materials with high thermal stability have a decisive influence on the lifetime and stability of OLED devices.An organic light-emitting material having high thermal stability,delayed fluorescence and room temperature phosphorescence emission characteristics is prepared by condensation reaction of a 3,3'-diaminobenzidine compound with a benzils.The results of photophysical properties show that TPQB and TPQB-OMe have delayed emission and room temperature phosphorescence.The thermal decomposition temperatures of TPQB and TPQB-OMe reach 384.11 and 416.86 ?, respectively,and there is no significant glass-transition temperature below 280 ?,showing a higher thermal stability.(3)The carbonyl group has a function of promoting intersystem crossing and enhancing phosphorescence emission.The condensation reaction of diaminobenzophenone with benzil was carried out to obtain a pyrazine compound containing a carbonyl group.The results show that both DPQPM and DPQPM-OMe have long-lived delayed fluorescence and room temperature phosphorescence characteristics;The emission spectra peaks of before and after stimulated by external force samples were 495/420 nm and 481/470 nm, respectively,which showed the phenomenon of blue-shift of force-induced luminescence.The quantum efficiency of DPQPM-OMe compound increased from 4.52% to 11.94% after force stimulation,showing enhanced stimuli effect;combined with experimental and theoretical calculations,the luminescence blue shift is because the triplet quenching is converted from phosphorescence to fluorescence emission.The luminescence enhancement is due to the planarization of the twisted configuration,which leads to an increase in the degree of conjugation,an increase in rigidity,and an increase in luminous efficiency.