title: Highly phosphorescent iridium complexes with chromophoric 2-(2-hydroxyphenyl)oxazole-based ancillary ligands: interligand energy-harvesting phosphorescence.
abstract: We disclose a controlled phosphorescence color tuning in a series of cyclometalated heteroleptic IrIII complexes (IrIII bis(2-(2,4-difluorophenyl)pyridinato- C,N (2'))(LX)) containing chromophoric 2-(2-hydroxyphenyl)oxazole-derivative ancillary ligands (LX). From a cyclometalated chloride-bridged IrIII dimer, three highly emissive cyclometalated heteroleptic IrIII complexes were obtained in good yields, each with a different conjugative plane in the chromophoric ancillary ligand (i.e., 2-(2-hydroxyphenyl)-4-methyloxazole, 2-(2-hydroxyphenyl)-6-methylbenzoxazole, and 2-(2-hydroxyphenyl)naphthoxazole). The three IrIII complexes showed highly efficient greenish blue (500 nm), green (525 nm), and yellow (552 nm) phosphorescence, respectively; a regular ca. 0.11 eV bathochromic shift was observed for each additional phenyl ring fused to the oxazole ring in the ancillary ligand. From the absorption, electrochemical measurements, static and transient photoluminescence (PL), and time-dependent density functional theory (TD-DFT) calculations, it can be concluded that the IrIII complexes have a single emission center with dual excitation paths. Finally, this characteristic energy-harvesting phosphorescence was further demonstrated in electrophosphorescence devices.
authors.affiliation: Department of Materials Science & Engineering, Seoul National University, San 56-1, Shillim-Dong, Kwanak-Gu, Seoul 151-744, Korea.
authors.forename: Youngmin
authors.initials: Y
authors.lastname: You
authors.forename: Jangwon
authors.initials: J
authors.lastname: Seo
authors.forename: Se Hun
authors.initials: SH
authors.lastname: Kim
authors.forename: Kil Suk
authors.initials: KS
authors.lastname: Kim
authors.forename: Tae Kyu
authors.initials: TK
authors.lastname: Ahn
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim
authors.forename: Soo Young
authors.initials: SY
authors.lastname: Park