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Simple Tuning of the Optoelectronic Properties of Ir III and Pt II Electrophosphors Based on Linkage Isomer Formation with a Naphthylthiazolyl Moiety
Author(s) -
Xu Xianbin,
Zhao Yongbiao,
Dang Jingshuang,
Yang Xiaolong,
Zhou Guijiang,
Ma Dongge,
Wang Lixiang,
Wong WaiYeung,
Wu Zhaoxin,
Zhao Xiang
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201200064
Subject(s) - chemistry , moiety , linkage isomerism , bathochromic shift , homoleptic , phosphorescence , ligand (biochemistry) , electroluminescence , quantum efficiency , photoluminescence , phosphor , stereochemistry , crystallography , fluorescence , quantum yield , chromophore , photochemistry , organic chemistry , optoelectronics , biochemistry , physics , receptor , layer (electronics) , quantum mechanics , metal
By tuning the substitution position of a thiazolyl group on the naphthalene system (α or β site), the distinctive electronic structures associated with these functional ligands have a substantial influence on both the photophysical behavior and electroluminescent (EL) performance of the resulting linkage isomers for two series of Ir III and Pt II phosphorescent emitters. The photoluminescence wavelength can be redshifted by ca. 23 nm for the linkage isomers upon replacing the β‐substituted thiazolyl‐based ligand with its α‐substituted counterpart in the homoleptic series of Ir III phosphors. Furthermore, the bathochromic effect can be as much as ca. 42 nm for the heteroleptic Ir III phosphors and ca. 59 nm for the Pt II compounds. Similarly, metallophosphors that bear β‐substituted ligands exhibit a different EL performance with respect to that of their linkage isomers with α‐substituted ligands. The best EL results associated with the triplet emitters chelated with β‐substituted ligands show a maximum brightness ( L max ) of 22563 cd m –2 , an external quantum efficiency ( η ext ) of 12.88 %, a luminance efficiency ( η L ) of 30.84 cd A –1 , and a power efficiency ( η p ) of 26.17 lm W –1 , whereas the EL performance of their α‐counterparts was characterized by a peak L max of 8653 cd m –2 , η ext of 6.18 %, η L of 8.55 cd A –1 , and η p of 6.54 lm W –1 . Owing to its unique electronic structure, the thiazolyl group is a good alternative to the pyridyl moiety to improve the EL performance of the metallophosphor. We have also demonstrated a simple and useful route to tune the functional properties of cyclometalated triplet emitters for EL applications.