Synthesis And Characterization Of Thiophene Triphosphine,Benzothiophene Diphosphine Copper(?) Halide Complexes And Dimethylfluorene Phosphine Copper(?) Iodide Cluster

The materials applied in organic light-emitting diodes(OLEDs)are mainly complexes of precious metals such as platinum and iridium.These precious metal raw materials are highly emissive,but scarce and expensive.Metal copper is rich and cheap,and copper(?)complexes with thermally activated delayed fluorescence(TADF)can reach a theoretical 100%quantum efficiency.But the quantum efficiencies of Cu(?)complexes are still need to be enhanced,specially for the light emitting except green materials.Here,rigid and electron-rich thiophene,benzothiophene and highly emissive blue material fluorene were selected to construct building block,three rigid tri-,di-and mono-phosphine ligands were synthesized and reacted with copper(?)halide to form a series of complexes 1-6 and a copper iodide cluster 7.These complexes were characterized by nuclear magnetic resonance(NMR),mass spectrometry(MS),infrared spectrum(IR),X-ray single crystal diffraction,ultraviolet-visible spectrum(UV-vis),fluorescence spectrum,and thermogravimetric analysis(TGA).Their structures were confirmed,and their photophysical properties and thermal stability were studied.(1)This chapter introduces the structure of OLED,luminescent materials and principles,the factors that affect the efficiencies of TADF,and currently,the research progress of copper(?)complexes applied in OLEDs.Based on the current research status in this field,the research content of this paper is proposed.(2)In this chapter,a new triphosphine ligand tpth,was designed and synthesized,and reacted with copper(?)halide to synthesize complexes 1-3.Complexes 1 and 2 are mononuclear four-coordinate structures.These complexes in powder state emit green and yellow-green light at room temperature.The maximum emission wavelengths are from 509 to550 nm,and the lifetimes are in the microsecond range(?=3.9-13.3?s),and the absolute quantum efficiencies are from 0.04 to 0.27.The luminescences are originated from metal-to-ligand charge transfer(MLCT),halogen-to-ligand charge transfer(XLCT),and intraligand charge transfer(ILCT).The small value of energy gap?E(S₁-T₁)in the solid state and the large difference in lifetimes at room temperature and low temperature indicates that they display TADF at room temperature.(3)In this chapter,a new bidentate ligand dpbt was designed and synthesized,and reacted with Cu(?)halide to synthesize three four-coordinate dinuclear halide copper(?)complexes[Cu X(dpbt)]₂.The crystal structures show that two copper atoms bridge-linked two halogen atoms,forming a Cu₂X₂twisted four-membered ring structures.These complexes in powder state emit yellow-green and orange light at room temperature.The maximum emission wavelengths are from 556 to 606 nm,the lifetimes are from 2.7 to 3.4?s,and the absolute quantum efficiencies are in the range of 0.54-0.86.The luminescences come from MLCT,XLCT,and ILCT.Three complexes show TADF and good thermal stability.(4)In this chapter,a new monophosphine ligand bis(9,9-dimethyl-2-fluorenyl)phenylphosphine(bmfp)was designed and synthesized,and reacted with Cu(?)iodide to synthesize a cubic cluster[Cu₄I₄(bmfp)₄].This cluster in powder state emits pink light at room temperature with the maximum emission wavelength 704 nm and lifetime 5.1?s,and its absolute quantum efficiency is 0.01.The luminescence is originated from MLCT and XLCT.The large difference in lifetimes between room temperature and low temperature provides evidence for TADF.