Blue Phosphorescent Zwitterionic Iridium(III) Complexes Featuring Weakly Coordinating nido-Carborane-Based Ligands
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- 作者：Jonathan C. Axtell ; Kent O. Kirlikovali ; Peter I. Djurovich ; Dahee Jung ; Vinh T. Nguyen ; Brian Munekiyo ; A. Timothy Royappa ; Arnold L. Rheingold ; Alexander M. Spokoyny
- 刊名：Journal of the American Chemical Society
- 出版年：2016
- 出版时间：December 7, 2016
- 年：2016
- 卷：138
- 期：48
- 页码：15758-15765
- 全文大小：652K
- ISSN：1520-5126
文摘
We report the development of a new class of phosphorescent zwitterionic bis(heteroleptic) Ir(III) compounds containing pyridyl ligands with weakly coordinating nido-carboranyl substituents. Treatment of phenylpyridine-based Ir(III) precursors with C-substituted ortho-carboranylpyridines in 2-ethoxyethanol results in a facile carborane deboronation and the formation of robust and highly luminescent metal complexes. The resulting nido-carboranyl fragments associate with the cationic Ir(III) center through primarily electrostatic interactions. These compounds phosphoresce at blue wavelengths (450–470 nm) both in a poly(methyl methacrylate) (PMMA) matrix and in solution at 77 K. These complexes display structural stability at temperatures beyond 300 °C and quantum yields greater than 40%. Importantly, the observed quantum yields correspond to a dramatic 10-fold enhancement over the previously reported Ir(III) congeners featuring carboranyl-containing ligands in which the boron cluster is covalently attached to the metal. Ultimately, this work suggests that the use of a ligand framework containing a weakly coordinating anionic component can provide a new avenue for designing efficient Ir(III)-based phosphorescent emitters.