Ligand Design and Preparation, Photophysical Properties, and Device Performance of an Encapsulated-Type Pseudo-Tris(heteroleptic) Iridium(III) Emitter

Abstract

The organic molecule 2-(1-phenyl-1-(pyridin-2-yl)­ethyl)-6-(3-(1-phenyl-1-(pyridin-2-yl)­ethyl)­phenyl)­pyridine (H 3 L) has been designed, prepared, and employed to synthesize the encapsulated-type pseudo-tris­(heteroleptic) iridium­(III) derivative Ir­(κ6-fac-C,C′,C″-fac-N,N′,N″-L). Its formation takes place as a result of the coordination of the heterocycles to the iridium center and the ortho-CH bond activation of the phenyl groups. Dimer [Ir­(μ-Cl)­(η4-COD)]2 is suitable for the preparation of this compound of class [Ir­(9h)] (9h = 9-electron donor hexadentate ligand), but Ir­(acac)3 is a more appropriate starting material. Reactions were carried out in 1-phenylethanol. In contrast to the latter, 2-ethoxyethanol promotes the metal carbonylation, inhibiting the full coordination of H 3 L. Complex Ir­(κ6-fac-C,C′,C″-fac-N,N′,N″-L) is a phosphorescent emitter upon photoexcitation, which has been employed to fabricate four yellow emitting devices with 1931 CIE (x:y) ∼ (0.52:0.48) and a maximum wavelength at 576 nm. These devices display luminous efficacies, external quantum efficiencies, and power efficacies at 600 cd m–2, which lie in the ranges 21.4–31.3 cd A–1, 7.8–11.3%, and 10.2–14.1 lm W1–, respectively, depending on the device configuration.

Encapsulated-Type Iridium(III) Phosphorescent Emitters with a Hexadentate Ligand of Three Different Bidentate Units

“…Voltammograms (Figure S13) were recorded in acetonitrile under argon using [Bu 4 N]­PF 6 as supporting electrolyte (0.1 M). They show a quasi-reversible oxidation from Ir­(III) to Ir­(IV) at potentials of 0.15 ( 5 ) and 0.13 ( 6 ) V vs Fc/Fc + , which compare well with that measured for the oxidation of 2 (0.14 V vs Fc/Fc + ) . Reductions were not observed in the range of the solvent window.…”

“…They show a quasi-reversible oxidation from Ir(III) to Ir(IV) at potentials of 0.15 (5) and 0.13 (6) V vs Fc/Fc + , which compare well with that measured for the oxidation of 2 (0.14 V vs Fc/Fc + ). 6 Reductions were not observed in the range of the solvent window.…”

“…This molecule was subsequently used to generate compound 2. 6 The iridium(III) center of this emitter is encapsulated by the orthometalated moieties derived from the fragments 2-phenylpyridine and 2-benzylpyridine. 7 Thus, complex 2 represents the first encapsulated emitter that is formally tris-heteroleptic since the 2-benzylpyridine fragments are formally different because they are attached to different groups, phenyl and pyridyl, although it is actually a model of bis-heteroleptic emitter of the class [3b+3b+3b′] (Scheme 1a).…”

“…In accordance with this approach, we recently designed and prepared proligand 1 ; it can be seen as a 2-phenylpyridine joined via the phenyl and pyridyl units to the methylene groups of two benzylpyridines, which bear a methyl substituent on the benzylic carbon atom. This molecule was subsequently used to generate compound 2 . The iridium­(III) center of this emitter is encapsulated by the orthometalated moieties derived from the fragments 2-phenylpyridine and 2-benzylpyridine .…”

Theoretical investigation of the influence of heterocycles on the radiative and non-radiative decay processes of iridium(iii) complexes

“…Because of their good color purities, high quantum efficiencies, relatively short phosphorescence lifetimes and high thermal stabilities, iridium(III) complexes are being applied as phosphorescent materials for OLEDs. [1][2][3][4][5][6][7][8][9][10][11] For Ir(III)cyclometalate complexes, the metal-to-ligand charge transfer ( 3 MLCT) involved in the emissive triplet excited state and the rigid octahedral structure can effectively facilitate the radiative decay process and suppress the non-radiative decay route. In addition, the color purities of iridium(III) complexes can be tuned via the addition of various substituents.…”