Study On Properties Of Phosphorescent Quinoxaline Derivatives-Iridium (Ⅲ) Metal Complexes

The research of organic light-emitting devices (OLED) has gone into a new era, and study on phosphorescent light-emitting materials and devices has been more and more popular, since Forrest found that, as efficient electrophosphorescent materials, heavy metal complexes could use both singlet and triplet excitons, and broke through the limitation that the quantum efficiency of electroluminescent materials only less than 25%, which could reach 100% at most.In this thesis, through molecular design, phosphorescent quinoxaline derivatives-iridium (III) metal complexes were synthesized:1.As organic main ligands,2,3-diphenyl-quinoxaline (DPQ) and its clorin brige of dimmer [Ir(DPQ)2Cl]2 were synthesized;2.Three kinds of pyrimidine series auxiliary ligands as follows:4-phenyl-pyrimidine (PPM), 4-(4-fluorophenyl) pyrimidine (FPPM),4-(2,4-difluorophenyl) pyrimidine (DFPPM) were synthesized. The five factors effecting on compounds'yield were investigated,including the kind of catalyst, catalyst molar ratio on ketone, reaction temperature and time, and the choice of elution agent in the separation process, by a single principle of variable. The optimum reaction conditions were discussed as follow:as PPM, when the molar ratio of CuCl to ketone was 0.65:1, reacting 15h under 170℃. Using diethyl ether anhydrous as eluent, and separating. Under this optimum conditions, the yield was 52%; as for FPPM and DFPPM, when the molar ratio of CuCl to ketone was 0.65:1, reacting 17h under 180℃. The different was:using 9:1 (diethyl ether anhydrous)-acetone mixture as eluent to separate FPPM, while using 4:1of that mixture as eluent to separate DFPPM. The yield respectively were 37% and 30%;3.Several phosphorescent metal complexes as follow:(DPQ)2IrCl(PPM), (DPQ)2IrCl(FPPM), (DPQ)2IrCl(DFPPM) and (DPQ)2IrCl(PPY) were newly synthesized.4.Rutin, which is a common kind of natural flavonoids, was used to insteading of the synthesized organic auxiliary ligands for the first time. Reacting it with quinoxaline into iridium (Ⅲ) metal complexes (DPQ)2IrCl(Rutin);Proof their structures by melting point, elemental analysis and nuclear magnetic resonance. Their absorption spectra and photoluminescence spectra were measured by UV-visible spectroscopy and fluorescence spectroscopy. Comparing to the spectra, discuss how the molecular structures of ligands, including main and auxiliary ligands, impact on electrophosphorescent emission properties of metal complexes. The following conclusions were found: (1) The bigger the main ligand conjugate system is, the greater its metal complex's emission wavelength moves to long-wave, which is called red shift.(2) When the substituent group on auxiliary ligands is exclusion of electronic, its metal complex's emission wavelength will move to long-wave; when the substituent group is electron-withdrawing, its metal complex's emission wavelength will move to short-wave, that is, blue shift. And the more intense the ability of electron-withdrawing is, the more obvious the move is.(3) Enlarging conjugate system of auxiliary ligands also can make metal complex's emission wavelength moved to long-wave.(4) Studies showed that, natural flavonoids with a large conjugated structure, and containing 3-hydroxyl or 5-hydroxyl substituents can form both oxygen-oxygen and oxygen-metal coordination with metal ions. It is a good kind auxiliary ligand of phosphorescent materials.