Iridium(III) Sensitisers and Energy Upconversion: The Influence of Ligand Structure upon TTA-UC Performance

Christopher E. Elgar; Haleema Y. Otaif; Xue Zhang; Jianzhang Zhao; Peter N. Horton; Simon J. Coles; Joseph M. Beames; Simon J.A. Pope

doi:10.1002/chem.202004146

Iridium(III) Sensitisers and Energy Upconversion: The Influence of Ligand Structure upon TTA-UC Performance

Christopher E. Elgar, Haleema Y. Otaif, Xue Zhang, Jianzhang Zhao, Peter N. Horton, Simon J. Coles, Joseph M. Beames^*, Simon J.A. Pope^*

^*Corresponding author for this work

Chemistry

Research output: Contribution to journal › Article › peer-review

14 Citations (Scopus)

Abstract

Six substituted ligands based upon 2-(naphthalen-1-yl)quinoline-4-carboxylate and 2-(naphthalen-2-yl)quinoline-4-carboxylate have been synthesised in two steps from a range of commercially available isatin derivatives. These species are shown to be effective cyclometallating ligands for Ir^III, yielding complexes of the form [Ir(C^N)₂(bipy)]PF₆ (where C^N=cyclometallating ligand; bipy=2,2′-bipyridine). X-ray crystallographic studies on three examples demonstrate that the complexes adopt a distorted octahedral geometry wherein a cis-C,C and trans-N,N coordination mode is observed. Intraligand torsional distortions are evident in all cases. The Ir^III complexes display photoluminescence in the red part of the visible region (668–693 nm), which is modestly tuneable through the ligand structure. The triplet lifetimes of the complexes are clearly influenced by the precise structure of the ligand in each case. Supporting computational (DFT) studies suggest that the differences in observed triplet lifetime are likely due to differing admixtures of ligand-centred versus MLCT character instilled by the facets of the ligand structure. Triplet–triplet annihilation upconversion (TTA-UC) measurements demonstrate that the complexes based upon the 1-naphthyl derived ligands are viable photosensitisers with upconversion quantum efficiencies of 1.6–6.7 %.

Original language	English
Pages (from-to)	3427-3439
Number of pages	13
Journal	Chemistry - A European Journal
Volume	27
Issue number	10
Early online date	26 Nov 2020
DOIs	https://doi.org/10.1002/chem.202004146
Publication status	Published - 15 Feb 2021

Bibliographical note

Funding Information:
Cardiff University (Knowledge Economy Skills Scholarship, via the Welsh Government's European Social Fund, to C.E.E.) and STG Aerospace (Drs. Sean O'Kell and Andrew Hallett) are thanked for financial support. We thank the staff of the Engineering and Physical Sciences Research Council (EPSRC) Mass Spectrometry National Service (Swansea University) for providing MS data and the Engineering and Physical Sciences Research Council (EPSRC) UK National Crystallographic Service at the University of Southampton.

Publisher Copyright:
© 2020 Wiley-VCH GmbH

Keywords

density functional theory
iridium complexes
phosphorescent species
spectroscopy
upconversion

ASJC Scopus subject areas

Catalysis
Organic Chemistry

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10.1002/chem.202004146

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title = "Iridium(III) Sensitisers and Energy Upconversion: The Influence of Ligand Structure upon TTA-UC Performance",

abstract = "Six substituted ligands based upon 2-(naphthalen-1-yl)quinoline-4-carboxylate and 2-(naphthalen-2-yl)quinoline-4-carboxylate have been synthesised in two steps from a range of commercially available isatin derivatives. These species are shown to be effective cyclometallating ligands for IrIII, yielding complexes of the form [Ir(C^N)2(bipy)]PF6 (where C^N=cyclometallating ligand; bipy=2,2′-bipyridine). X-ray crystallographic studies on three examples demonstrate that the complexes adopt a distorted octahedral geometry wherein a cis-C,C and trans-N,N coordination mode is observed. Intraligand torsional distortions are evident in all cases. The IrIII complexes display photoluminescence in the red part of the visible region (668–693 nm), which is modestly tuneable through the ligand structure. The triplet lifetimes of the complexes are clearly influenced by the precise structure of the ligand in each case. Supporting computational (DFT) studies suggest that the differences in observed triplet lifetime are likely due to differing admixtures of ligand-centred versus MLCT character instilled by the facets of the ligand structure. Triplet–triplet annihilation upconversion (TTA-UC) measurements demonstrate that the complexes based upon the 1-naphthyl derived ligands are viable photosensitisers with upconversion quantum efficiencies of 1.6–6.7 %.",

keywords = "density functional theory, iridium complexes, phosphorescent species, spectroscopy, upconversion",

author = "Elgar, {Christopher E.} and Otaif, {Haleema Y.} and Xue Zhang and Jianzhang Zhao and Horton, {Peter N.} and Coles, {Simon J.} and Beames, {Joseph M.} and Pope, {Simon J.A.}",

note = "Funding Information: Cardiff University (Knowledge Economy Skills Scholarship, via the Welsh Government's European Social Fund, to C.E.E.) and STG Aerospace (Drs. Sean O'Kell and Andrew Hallett) are thanked for financial support. We thank the staff of the Engineering and Physical Sciences Research Council (EPSRC) Mass Spectrometry National Service (Swansea University) for providing MS data and the Engineering and Physical Sciences Research Council (EPSRC) UK National Crystallographic Service at the University of Southampton. Publisher Copyright: {\textcopyright} 2020 Wiley-VCH GmbH",

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AU - Zhao, Jianzhang

AU - Horton, Peter N.

AU - Coles, Simon J.

AU - Beames, Joseph M.

AU - Pope, Simon J.A.

N1 - Funding Information: Cardiff University (Knowledge Economy Skills Scholarship, via the Welsh Government's European Social Fund, to C.E.E.) and STG Aerospace (Drs. Sean O'Kell and Andrew Hallett) are thanked for financial support. We thank the staff of the Engineering and Physical Sciences Research Council (EPSRC) Mass Spectrometry National Service (Swansea University) for providing MS data and the Engineering and Physical Sciences Research Council (EPSRC) UK National Crystallographic Service at the University of Southampton. Publisher Copyright: © 2020 Wiley-VCH GmbH

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N2 - Six substituted ligands based upon 2-(naphthalen-1-yl)quinoline-4-carboxylate and 2-(naphthalen-2-yl)quinoline-4-carboxylate have been synthesised in two steps from a range of commercially available isatin derivatives. These species are shown to be effective cyclometallating ligands for IrIII, yielding complexes of the form [Ir(C^N)2(bipy)]PF6 (where C^N=cyclometallating ligand; bipy=2,2′-bipyridine). X-ray crystallographic studies on three examples demonstrate that the complexes adopt a distorted octahedral geometry wherein a cis-C,C and trans-N,N coordination mode is observed. Intraligand torsional distortions are evident in all cases. The IrIII complexes display photoluminescence in the red part of the visible region (668–693 nm), which is modestly tuneable through the ligand structure. The triplet lifetimes of the complexes are clearly influenced by the precise structure of the ligand in each case. Supporting computational (DFT) studies suggest that the differences in observed triplet lifetime are likely due to differing admixtures of ligand-centred versus MLCT character instilled by the facets of the ligand structure. Triplet–triplet annihilation upconversion (TTA-UC) measurements demonstrate that the complexes based upon the 1-naphthyl derived ligands are viable photosensitisers with upconversion quantum efficiencies of 1.6–6.7 %.

AB - Six substituted ligands based upon 2-(naphthalen-1-yl)quinoline-4-carboxylate and 2-(naphthalen-2-yl)quinoline-4-carboxylate have been synthesised in two steps from a range of commercially available isatin derivatives. These species are shown to be effective cyclometallating ligands for IrIII, yielding complexes of the form [Ir(C^N)2(bipy)]PF6 (where C^N=cyclometallating ligand; bipy=2,2′-bipyridine). X-ray crystallographic studies on three examples demonstrate that the complexes adopt a distorted octahedral geometry wherein a cis-C,C and trans-N,N coordination mode is observed. Intraligand torsional distortions are evident in all cases. The IrIII complexes display photoluminescence in the red part of the visible region (668–693 nm), which is modestly tuneable through the ligand structure. The triplet lifetimes of the complexes are clearly influenced by the precise structure of the ligand in each case. Supporting computational (DFT) studies suggest that the differences in observed triplet lifetime are likely due to differing admixtures of ligand-centred versus MLCT character instilled by the facets of the ligand structure. Triplet–triplet annihilation upconversion (TTA-UC) measurements demonstrate that the complexes based upon the 1-naphthyl derived ligands are viable photosensitisers with upconversion quantum efficiencies of 1.6–6.7 %.

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Iridium(III) Sensitisers and Energy Upconversion: The Influence of Ligand Structure upon TTA-UC Performance

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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