Abstract
Two new tfmpiq-based bis-cyclometalated iridium(III) complexes, [(tfmpiq)2Ir(imdzppo)] (2a) and [(tfmpiq)2Ir(idzpo)] (2b) (where tfmpiq = 1-(4-(trifluoromethyl)phenyl)isoquinoline, imdzppo = 2-(imidazo[1,2-a]pyridin-2-yl)phenol, idzpo = 2-(2H-indazol-2-yl)phenol), have been synthesized and fully characterized. The single crystal structure of 2b has been determined. The relationship between the structures and photophysical properties of both complexes are considered, and the DFT calculations have been used to further support the deduction. These Ir(III) complexes emit red light with quantum yields of 39.9-51.9% in degassed CH2Cl2 solution at room temperature. Also, their emission originates from a hybrid 3MLCT/3LLCT/3LC excited state. All these results show that iridium(III) complexes 2a-2b are suitable for red-phosphorescent materials in OLEDs.
Highlights
The LANL2DZ basis set was used for the iridium(III), whereas the 6-31G* basis set was adopted for the ligands
Solvent effects were considered within the SCRF theory using the polarized continuum model (PCM) approach to model the interaction with the solvent.[30,31]
Scheme 1 outlines the synthetic routes for iridium complexes 2a–2b investigated in this work
Summary
Organic light-emitting diodes (OLEDs) have attracted great attention on the development of modern optoelectronic technologies such as full-color displays and solid-state lighting sources.[1,2,3] cyclometalated iridium(III) complexes ([Ir(C^N)3] or [(C^N)2Ir(LX)]) are the most valuable emitting materials in the fabrication of OLEDs, owing to their relatively short excited-state lifetime, high phosphorescence efficiency and excellent color-tuning capability.[4,5] As compared to other colors, red electrophosphorescent emitting phosphors are difficult to maintain high device efficiency, since their quantum efficiencies tend to decrease as the emission wavelength increases in accordance with the energy gap law.[6,7,8] the design and syntheses of highly efficient red-emitting iridium complexes remain a challenge.1-Phenylisoquinoline (piq) is one typical ligand framework to construct red iridium complexes. A large number of piq-based Ir(III) complexes have been reported during the past decade.[9,10,11,12,13] Among these examples, iridium complexes of fluorinated phenylisoquinoline show strong electroluminescence brightness and efficiency. This is because the fluorine groups could modify the electronic properties and decrease the rate of nonradioactive deactivation and improve phosphorescence quantum yields.[14] in 2006, K.-H.
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