122nd General Meeting of the KCS

Type Poster Presentation
Area Industrial Chemistry
Room No. Grand Ballroom
Time 10월 19일 (금요일) 11:00~12:30
Code IND.P-24
Subject Synthesis and characterization of heteroleptic cyclometalated Ir(III) complexes substituted with 2-(2-sulfonylfluorophenyl)pyridine (ppySO2F) ligand for blue phosphorescent organic-light-emitting diodes
Authors Jin-Hyoung Kim, So-Yoen Kim, Dae won Cho*, Sang Ook Kang, Ho-Jin Son*
Department of Advanced Materials Chemistry, Korea University, Korea
Abstract In order to understand the intrinsic nature of nonradiative processes in heteroleptic cyclometalated Ir(III) complexes, highly phosphorescent Ir3+ complexes containing 2-(2-sulfonylfluorophenyl)pyridine (ppySO2F) as the cyclometalated ligand were newly synthesized. Three ancillary ligands, acetylacetonate (acac), picolinate (pic), and tetrakis-pyrazolyl borate (bor), were employed for the preparation of the Ir(III) complexes [Ir(ppySO2F)2(acac)] (Ir-acac), [Ir(ppySO2F)2(pic)] (Ir-pic), and [Ir(ppySO2F)2(bor)] (Ir-bor). The molecular structures were characterized by X-ray crystallography. Blue phosphorescence maxima were observed at 458, 466, and 478 nm for Ir-bor, Ir-pic, and Ir-acac, respectively, at 77 K, and the corresponding emission quantum yields were determined to be 0.79, 0.80, and 0.98 in anaerobic CH2Cl2 at 300 K. Additionally, the phosphorescence decay times were measured to be 1.27, 2.11, and 3.58 μs for Ir-acac, Ir-pic, and Ir-bor, respectively. No temperature dependence was observed for the emission lifetimes in 298-338 K. These results indicate that there is no activation barrier to crossing to a nonradiative state like metal-centered (MC, d-d) state. The radiative rate constants (kr) are within a narrow range of 3.0–5.5 × 10-5 s-1. However, the nonradiative rate constants (knr) are within a wide range of 14.2–0.52 × 10-4 s-1. The knr values showed linear correlation with the energy gap. We carried out ab initio calculations to evaluate the energy states and their corresponding orbitals. The nonemissive MC states lie at higher energies than the emissive MLCT state, hence the MC states can be excluded from the nonradiative pathway.
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