The Synthesis And Properties Study Of Organic Binuclear Cyclometalated Iridium Complexes Phosphorescent Material With The Bradge Of Phenyl Oxdizole/carbazole-based Picolinic Acid

The status of organic electrophosphorescent materials and their devices were reviewed in this dissertation. The synthesis and optpelectronic properties of the dinuclear cyclometalated iridium complexes containing various ancillary ligands of picolinic acid derivatives bridged with oxadiazole or carbazole group by alkoxy group have been carried out in order to solve current issues in the organic white electrophosphorescent materials and their white organic light-emitting diodes. The key studies are listed below.1. Ancillary ligands of picolinic acid derivatives have been obtained in which an oxadizole or carbazole moiety is attached to the picolic acid via a nonconjugated alkoxy group. These ligands were synthesized by etherifying reaction between hydroxy picolic acid derivatives and aryl oxadiazoles and carbazole derivatives containing various substituent group. The influence of reaction conditions on synthesis of these ligands was studied. The key conditions of the condensation of diacylhydrazine and the esterifying reaction were optimized.2. The dinuclear cyclometalated iridium complexes bridged with oxadiazole or carbazole group by nonconjugated effect of alkoxy group have been achieved. Nine kinds of these dinuclear cyclometalatedr iridium complexes were synthesized choosing tetra(2,4-diflurophenyl pyridine-N,C2')(μ-dichlorine) bi-iridium(III) and tetra(1-phenylisoquinoline-N,C2')(μ-dichlorine) bi-iridium(III) as raw materials, respectively. These dinuclear cyclometalated iridium complexes contain red-emitting dichromophores or blue-emitting dichromophores or mixing red- and blue-emitting dichromophores.3. The UV-vis, photoluminescence and electrochemical properties of these dinuclear cyclometalatedr iridium complexes were studied. The results were shown as the follow: (1) Oxadiazole or carbazole group has a little influence on the UV-vis, photoluminescence properties of its dinuclear cyclometalatedr iridium complexes due to the isolating effect of the alkoxy group. These UV-vis and photoluminescence properties of the dinuclear cyclometalatedr iridium complexes mainly depend on the red- and blue-emitting dichromophores in the complexes. For the dinuclear cyclo -metalated iridium complexes containing blue-emitting dichromophores, a UV absorption peak at 389 nm and a maximum photoluminescence peak at 471 nm were observed. For the dinuclear cyclometalated iridium complexes containing red-emitting dichromophores, a UV absorption peak at 462 nm and a maximum photoluminescence peak at 612 nm were displayed. For the dinuclear cyclometalated iridium complexes containing mixing red- and blue-emitting, a UV absorption peak at 462 nm and two photoluminescence peak at 472 nm and 612 nm were presented, in which the UV absorption peak is attributed to the metal-ligand charge transfer (MLCT) transition. Photoluminescence emission from 460 nm and 750 nm indicates that this kind of dinuclear cyclometalated iridium complexes containing mixing red- and blue-emitting can emit light with broad spectrum. (2) The electrochemical properties of these dinuclear cyclometalated iridium complexesare related to the red- and blue-emitting dichromophores, as well as oxadiazole and carbazole groups in the complexes.4. The electroluminescent properties of these dinuclear cyclometalated iridium complexes were also studied. Single-layered polymer light-emittin devices (PLEDs) were fabricated using these dinuclear cyclometalated iridium complexes containing mixing red- and blue-emitting as dopant and a blend of poly(vinylcarbazole) and 2-tert-butylphenyl-5-biphenyl -1,3,4-oxadiazoles as host materials . The maximum external quantum efficiency of 1.2% and brightness of 1350 cd/m2 were achieved in these devices. While the dopant concentration low than 1%, the device emited light with broad spectrum.5. This investigation laid a good foundation for further studying electro -phosphorescent materials emitting with broad spectral band and their white-emitting PLEDs with excellent luminescent properties.