Excited state lifetime modulation by twisted and tilted molecular design in carbene-metal-amide photoemitters

Gu, Qinying, Chotard, Florian, Eng, Julien, Reponen, Antti-Pekka M., Vitorica-Yrezabal, Inigo J., Woodward, Adam W., Penfold, Thomas J., Credgington, Dan, Bochmann, Manfred ORCID: https://orcid.org/0000-0001-7736-5428 and Romanov, Alexander S. (2022) Excited state lifetime modulation by twisted and tilted molecular design in carbene-metal-amide photoemitters. Chemistry of Materials, 34 (16). 7526–7542. ISSN 0897-4756

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Abstract

Carbene-metal-amides (CMAs) are an emerging class of photoemitters based on a linear donor-linker-acceptor arrangement. They exhibit high flexibility about the carbene-metal and metal-amide bonds, leading to a conformational freedom which has a strong influence on their photophysical properties. Herein we report CMA complexes with (1) nearly coplanar, (2) twisted, (3) tilted, and (4) tilt-twisted orientations between donor and acceptor ligands and illustrate the influence of preferred ground-state conformations on both the luminescence quantum yields and excited-state lifetimes. The performance is found to be optimum for structures with partially twisted and/or tilted conformations, resulting in radiative rates exceeding 1 × 10 6s -1. Although the metal atoms make only small contributions to HOMOs and LUMOs, they provide sufficient spin-orbit coupling between the low-lying excited states to reduce the excited-state lifetimes down to 500 ns. At the same time, high photoluminescence quantum yields are maintained for a strongly tilted emitter in a host matrix. Proof-of-concept organic light-emitting diodes (OLEDs) based on these new emitter designs were fabricated, with a maximum external quantum efficiency (EQE) of 19.1% with low device roll-off efficiency. Transient electroluminescence studies indicate that molecular design concepts for new CMA emitters can be successfully translated into the OLED device.

Item Type: Article
Additional Information: Funding Information: This work was supported by the Engineering and Physical Sciences Research Council (EPSRC, grant no. EP/M005143/1, EP/R021503/1 and EP/P012388/1), the Royal Society, the European Research Council (ERC) and Samsung Display Corp. (SDC). M.B. is an ERC Advanced Investigator Award holder (grant no. 338944-GOCAT). D.C. acknowledges support from the Royal Society (grant nos. UF130278 and RG140472). A.S.R. acknowledges support from the Royal Society (grant nos. URF\R1\180288 and RGF\EA\181008). The authors thank the National Mass Spectrometry Facility at Swansea University for measurements.
Uncontrolled Keywords: gold complexes,photoluminescence,light emitting diodes,organometallics,materials chemistry,chemical engineering(all),chemistry(all) ,/dk/atira/pure/subjectarea/asjc/2500/2505
Faculty \ School: Faculty of Science > School of Chemistry
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Depositing User: LivePure Connector
Date Deposited: 09 Sep 2022 16:30
Last Modified: 05 Oct 2022 00:17
URI: https://ueaeprints.uea.ac.uk/id/eprint/88065
DOI: 10.1021/acs.chemmater.2c01938

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