Bond fission and non-radiative decay in iridium(III) complexes

Zhou, Xiuwen, Burn, Paul L. and Powell, Benjamin J. (2016) Bond fission and non-radiative decay in iridium(III) complexes. Inorganic Chemistry, 55 11: 5266-5273. doi:10.1021/acs.inorgchem.6b00219

Author Zhou, Xiuwen
Burn, Paul L.
Powell, Benjamin J.
Title Bond fission and non-radiative decay in iridium(III) complexes
Journal name Inorganic Chemistry   Check publisher's open access policy
ISSN 1520-510X
Publication date 2016-05-13
Year available 2016
Sub-type Article (original research)
DOI 10.1021/acs.inorgchem.6b00219
Open Access Status Not Open Access
Volume 55
Issue 11
Start page 5266
End page 5273
Total pages 8
Place of publication Washington, DC, United States
Publisher American Chemical Society
Language eng
Subject 1606 Physical and Theoretical Chemistry
1604 Inorganic Chemistry
Abstract We investigate the role of metal ligand bond fission in the nonradiative decay of excited states in iridium(III) complexes with applications in blue organic light-emitting diodes (OLEDs). We report density functional theory (DFT) calculations of the potential energy surfaces upon lengthening an iridium-nitrogen (Ir-N) bond. In all cases we find that for bond lengths comparable to those of the ground state the lowest energy state is a triplet with significant metal-to-ligand change transfer character ((MLCT)-M-3). But, as the Ir-N bond is lengthened there is a sudden transition to a regime where the lowest excited state is a triplet with significant metal centered character ((MC)-M-3). Time-dependent DFT relativistic calculations including spin-orbit coupling perturbatively show that the radiative decay rate from the (MC)-M-3 state is orders of magnitude slower than that from the (MLCT)-M-3 state. The calculated barrier height between the 3MLCT and 3MC regimes is clearly correlated with previously measured nonradiative decay rates, suggesting that thermal population of the (MC)-M-3 state is the dominant nonradiative decay process at ambient temperature. In particular, fluorination both drives the emission of these complexes to a deeper blue color and lowers the (MLCT)-M-3-(MC)-M-3 barrier. If the Ir-N bond is shortened in the (MC)-M-3 state another N atom is pushed away from the Ir, resulting in the breaking of this bond, suggesting that once the Ir-N bond breaks the damage to the complex is permanent-this will have important implications for the lifetimes of devices using this type of complex as the active material. The consequences of these results for the design of more efficient blue phosphors for OLED applications are discussed.
Keyword Physical and Theoretical Chemistry
Inorganic Chemistry
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID FT130100161

Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
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School of Chemistry and Molecular Biosciences
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Citation counts: TR Web of Science Citation Count  Cited 16 times in Thomson Reuters Web of Science Article | Citations
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Created: Fri, 20 May 2016, 23:35:00 EST by Mrs Louise Nimwegen on behalf of School of Chemistry & Molecular Biosciences