title: Iridium(I) pyridyl azolate complexes with saturated red metal-to-ligand charge transfer phosphorescence; fundamental and potential applications in organic light-emitting diodes.
abstract: Preparation of a new series of neutral metal complexes [(cod)Ir(fppz)] (1), [(cod)Ir(bppz)] (2), [(cod)Ir(fptz)] (3) and [(cod)Ir(bptz)] (4), bearing one cod ligand and a pyridyl azolate chelate are reported. A single-crystal X-ray diffraction study of 3 reveals the expected distorted square-planar geometry. The lowest absorption band consists of IrI atom increased triplet dpi-->pi* transitions (3MLCT), the assignment of which is firmly supported by the theoretical approaches. Complexes 1-4 exhibit weak phosphorescence in degassed solution at room temperature, whereas much more intense, solid-state phosphorescence appears in the range 622-649 nm. The pure MLCT emission was used as a prototypical model to address its remarkable spectral differences from the IrIII isoquinoline pyrrolide complex (5), which has mainly 3pipi phosphorescence. Complex 3 was used as a dopant to fabricate red-emitting phosphorescent organic light-emitting diodes (OLEDs). For the 7 % doped device, a maximum brightness of 3010 cd m-2 was achieved at an applied voltage of 15 V and with CIE coordinates of (0.56, 0.33), demonstrating for the first time the potential of neutral IrI complexes in OLED applications.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan.
authors.forename: Chung-Hong
authors.initials: CH
authors.lastname: Fang
authors.forename: Yao-Lun
authors.initials: YL
authors.lastname: Chen
authors.forename: Cheng-Han
authors.initials: CH
authors.lastname: Yang
authors.forename: Yun
authors.initials: Y
authors.lastname: Chi
authors.forename: Yu-Shan
authors.initials: YS
authors.lastname: Yeh
authors.forename: Elisa Y
authors.initials: EY
authors.lastname: Li
authors.forename: Yi-Ming
authors.initials: YM
authors.lastname: Cheng
authors.forename: Chia-Jung
authors.initials: CJ
authors.lastname: Hsu
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
authors.forename: Chin-Ti
authors.initials: CT
authors.lastname: Chen