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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 11
BKCSDE 35(11)
November 20, 2014 

 
Title
Photophysical Properties of Highly Efficient Blue-Green Emitting Cationic Iridium (III) Complexes Containing Two 2-Phenylbenzothiazole Ligands and One Diphosphine Ligand
Author
Seong-Jae Yun, Young-Kwang Song, Minji Kim, Jaemin Shin, Sung-Ho Jin, Sung Kwon Kang, Young-Inn Kim*
Keywords
Cationic iridium complex, Blue-green phosphorescence, Phosphorescent iridium complex, Phosphorescent material, High quantum yield
Abstract
Two novel phosphorescent heteroleptic cationic Ir(III) complexes, Ir(bt)2(dmpe) (Ir1) and Ir (bt)2(dppe) (Ir2), where bt is 2-phenylbenzothiazole, dmpe is 1,2-bis(dimethylphosphino)ethane, and dppe is 1,2-bis(diphenylphosphino) ethane, were designed and synthesized. Their photophysical and electrochemical properties and the X-ray structure of the Ir1 complex were investigated. The prepared Ir(III) complexes exhibited blue-green emissions at 503-538 nm with vibronic fine structures in dichloromethane solution and PMMA film, implying that the lowest excited states are dominated by ligand-based 3π-π* transitions. The π-acceptor ability of the diphosphine ancillary ligand leads to blue-shift emission. The room temperature photoluminescent quantum yields (PLQYs) of Ir1 and Ir2 were 52% and 45%, respectively, in dichloromethane solution. These high PLQYs resulted from steric hindrances by the bulky cationic iridium complexes. The crystal structure of Ir1 was determined by X-ray crystallography, which revealed that central iridium adopted a distorted octahedral structure coordinated with two bt ligands (N^C) and one dmpe ligand (P^P) showing cis C-C and trans N-N dispositions. The bent nature of the dmpe ligand resulted in a relatively wide bite angle of 83.83o of P-Ir-P.
Page
3199 - 3204
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