Synthesis and their emission properties of Iridium(III) complex bearing trifluoromethyl(-CF3) moiety

초록

Recently, phosphorescence-based light-emitting diodes (LEDs) have attracted worldwide attention for their high emission efficiency[1]. External quantum efficiency exceeding 15% in multi-layer device structure with phosphorescent dye doped emitting layer has been demonstrated by Adachi et al.[2].Due to strong spin-orbital mixing of heavy-metal ions in phosphorescent dyes, both singlet and triplet excitons can be fully utilized. Thereby, for such phosphorescent dye doped devices internal quantum efficiency has potential of 100%. As shown in Fig.1, we proposed a series of novel iridium(III) complex bearing trifluoromethyl(-CF3) moiety. Trifluoromethyl moiety has two specific properties which are an electron-withdrawing group and a large bulky group. The former might induce the phosphorescence color change to shorter wavelength, the latter might reduce the aggregation self-queching effect[4,5]. Through the study on the emissive effect of the specific ligand, new ligands(bfp), 2-(4’-bromo-3’-trifluoromethylphenyl)pyridine, was designed and synthesized by the specific aromatic coupling method such as a diazonium coupling method. The iridium(III) complex beraing trifluoromethyl group . [Ir(bfp)2(acac)] was synthesized successfully and characterized by 1H-NMR, 13C-NMR, UV-Visible(UV) spectroscopy, photoluminesence(PL). In dichloromethane, this iridium complex exhibited an emission maximum at 530nm. Through suzuki coupling reaction with aromatic boronic acid, we observed the changes of emission properties. And, the solution processible phosphorescent polymers based on 9,9-dialkylfluorene repeat units in conjugation with [Ir(bfp)2(acac)] through Suzuki polycondensation reaction were synthesized and characterized their photophysical properties.