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Synthesis and luminescence properties of iridium complexes chelated with coumarin ligands.

Journal of nanoscience and nanotechnology (2013-07-19)
Hye Rim Park, Bo Young Kim, Young Kwan Kim, Yunkyoung Ha
ABSTRACT

According to a recent report, the organic light-emitting diodes (OLEDs) using the iridium complexes of coumarin derivatives as emissive dopants are highly efficient and stable. Unlike the other Ir(III) phopsphorescent dopants, these coumarin-based Ir(III) complexes can effectively trap and transport electrons in the emissive layer. We have prepared a series of phosphorescent cyclometalated Ir(III) complexes containing 3-(2-pyridinyl)coumarin (pc) as an ancillary ligand. The new heteroleptic iridium complexes, Ir(C--N)2(pc) (CAN = 2-(2,4-difluorophenyl)pyridine (F2-ppy), 2-phenylpyridine (ppy) and 2-phenylquinoline (pq)) were characterized by 1H NMR and mass spectrometer. As main ligands, F2-ppy, ppy and pq were employed, which should have the drastically different ligand molecular orbital energy levels. The iridium complexes showed various emission ranges from 560 to 610 nm, depending upon the relative energy levels of their main and ancillary ligands. The photoabsorption, photoluminescence and electroluminescence of the complexes were studied. We also investigated the electrochemical properties of the iridium complexes to compare the HOMO and LUMO energy levels of these phosphorescent materials.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Coumarin, ≥99% (HPLC)
Sigma-Aldrich
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Sigma-Aldrich
Coumarin, ≥98%
Supelco
Coumarin, certified reference material, TraceCERT®
Coumarin, primary reference standard
Sigma-Aldrich
Iridium, wire, diam. 0.15 mm, 99.9% trace metals basis
Sigma-Aldrich
Iridium, evaporation slug, diam. × L 0.6 cm × 1.2 cm, 99.9% trace metals basis
Sigma-Aldrich
Iridium, black, powder, −200 mesh, ≥99% trace metals basis
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Iridium, foil, thickness 0.25 mm, 99.9% trace metals basis