Details

Autor(en) / Beteiligte

• Hsieh, Cheng-Han
• Wu, Fang-Iy
• Fan, Chun-Hsiang
• Huang, Min-Jie
• Lu, Kun-Yi
• Chou, Pei-Yu
• Yang, Yu-Han Ou
• Wu, Shih-Hsiang
• Chen, I-Chia
• Chou, Shu-Hua
• Wong, Ken-Tsung
• Cheng, Chien-Hong

Titel

Design and Synthesis of Iridium Bis(carbene) Complexes for Efficient Blue Electrophosphorescence

Ist Teil von

• Chemistry : a European journal, 2011-08, Vol.17 (33), p.9180-9187

Ort / Verlag

Weinheim: WILEY-VCH Verlag

Erscheinungsjahr

2011

Quelle

Wiley Online Library - AutoHoldings Journals

Beschreibungen/Notizen

• Five iridium bis(carbene) complexes, [Ir(pmi)2(pypz)] (1), [Ir(mpmi)2(pypz)] (2), [Ir(fpmi)2(pypz)] (3), [Ir(fpmi)2(pyim)] (4), and [Ir(fpmi)2(tfpypz)] (5) (pmi=1‐phenyl‐3‐methylimdazolin‐2‐ylidene‐C,C2′; fpmi=1‐(4‐fluorophenyl)‐3‐methylimdazolin‐2‐ylidene‐C,C2′; mpmi=1‐(4‐methyl‐phenyl)‐3‐methylimdazolin‐2‐ylidene‐C,C2′; pypz=2‐(1H‐pyrazol‐5‐yl)pyridinato; pyim=2‐(1H‐imidazol‐2‐yl)pyridinato; and tfpypz=2‐(3‐(trifluoromethyl)‐1H‐pyrazol‐5‐yl)pyridinato), were synthesized and their structures were characterized by NMR spectroscopy, mass spectroscopy and X‐ray diffraction. These complexes showed phosphorescent emission with the emission maxima between 453 and 490 nm. Various spectrophotometric measurements, cyclic voltammetric studies, and density functional theory (DFT) calculations show that, unlike most of the phosphorescent cyclometalated iridium complexes, the lowest unoccupied molecular orbital (LUMO) energy and the emissive state of these iridium complexes are mainly controlled by the N,N′‐heteroaromatic (N^N) ligand. Despite the fact that the LUMO levels of these complexes are mainly on the N^N ligands, the efficiencies of the electroluminescent (EL) devices are very high. For example, the EL devices using [Ir(mpmi)2(pypz)], [Ir(fpmi)2(pypz)], and [Ir(fpmi)2(tfpypz)] as the dopant emitters exhibited light‐ to deep‐blue electrophosphorescence with external quantum efficiencies of 15.2, 14.1, and 7.6 % and Commission Internationale d’Énclairage (x,y) coordinates (CIEx,y) of (0.14, 0.27), (0.14, 0.18) and (0.14, 0.10), respectively. Simple and effective! Experimental and theoretical studies show that the emissive state of the iridium complexes (see figure) is mainly controlled by the single conjugated N,N′‐heteroaromatic ligand. Their emission color can be systematically tuned from light to deep blue by simple ligand modulation. The blue electrophosphorescent devices using these complexes as the emitter show very high external quantum efficiencies of 7.6–15.2 %.