title: Synthesis and properties of greenish-blue-emitting iridium dendrimers with N-phenylcarbazole-based polyether dendrons by a post-dendronization route.
abstract: A series of solution processible greenish-blue-emitting Ir dendrimers with polyether dendrons that consist of N-phenylcarbazole (NPC) are developed via a convenient post-dendronization method. It involves two steps: (i) the successful preparation of a reactive Ir core, namely m-HO-dfppyIr, only when the hydroxyl group is located at the meta position relative to the N atom in the C^N ligand so as to eliminate the possible resonance structure between enol and keto; and (ii) the subsequent functionalization with NPC-based polyether dendrons to afford the first, second and third generation Ir dendrimers (Ir-G1B, Ir-G2B and Ir-G3B) with ease and high yields over 60%. All these dendritic complexes possess good thermal stability with decomposition temperatures higher than 380 °C and glass transition temperatures higher than 200 °C. In addition, with the growing generation number, the intermolecular interactions between emissive Ir cores are expected to be effectively inhibited to avoid the luminescence quenching, which is confirmed from the blue-shifted emission peak and the enhanced lifetime of Ir-G3B in the solid state. As a result, on going from Ir-G1B to Ir-G3B, the maximum luminous efficiency rises upward from 4.7 to 9.2 cd A(-1) for nondoped electrophosphorescent devices. Further optimization by doping them into a dendritic H2 host leads to the improved luminous efficiencies as high as 20.0-25.2 cd A(-1).
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P. R. China. junqiaod@ciac.ac.cn lixiang@ciac.ac.cn.
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.forename: Shumeng
authors.initials: S
authors.lastname: Wang
authors.forename: Shiyang
authors.initials: S
authors.lastname: Shao
authors.forename: Junqiao
authors.initials: J
authors.lastname: Ding
authors.forename: Lixiang
authors.initials: L
authors.lastname: Wang
authors.forename: Xiabin
authors.initials: X
authors.lastname: Jing
authors.forename: Fosong
authors.initials: F
authors.lastname: Wang