Iridium(III) sensitisers and energy upconversion: the influence of ligand structure upon TTA-UC performance
Iridium(III) sensitisers and energy upconversion: the influence of ligand structure upon TTA-UC performance
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 %.
Density functional theory, iridium complexes, phosphorescent species, spectroscopy, upconversion
3427-3439
Elgar, Christopher E.
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Otaif, Haleema Y.
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Zhang, Xue
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Zhao, Jianzhang
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Horton, Peter
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Coles, Simon J.
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Beames, Joseph M.
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Pope, Simon J.A.
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15 February 2021
Elgar, Christopher E.
f59426b7-72ba-4125-96e3-b9b63da790ff
Otaif, Haleema Y.
1b365536-1683-40d5-b6d2-3f869cdac579
Zhang, Xue
254d4526-6dd3-4560-8e3d-7725a5f6f07c
Zhao, Jianzhang
08415724-251c-475a-97d7-bb21408eb959
Horton, Peter
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Beames, Joseph M.
73b04545-4859-44ad-999e-551f82924c29
Pope, Simon J.A.
db9a489c-29ba-41cd-a96a-623bace0889d
Elgar, Christopher E., Otaif, Haleema Y., Zhang, Xue, Zhao, Jianzhang, Horton, Peter, Coles, Simon J., Beames, Joseph M. and Pope, Simon J.A.
(2021)
Iridium(III) sensitisers and energy upconversion: the influence of ligand structure upon TTA-UC performance.
Chemistry - A European Journal, 27 (10), .
(doi:10.1002/chem.202004146).
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 %.
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More information
Accepted/In Press date: 26 November 2020
e-pub ahead of print date: 19 January 2021
Published date: 15 February 2021
Additional Information:
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.
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
Identifiers
Local EPrints ID: 447523
URI: http://eprints.soton.ac.uk/id/eprint/447523
ISSN: 0947-6539
PURE UUID: bcfeddf3-3727-4c40-8c8c-4ba67573a4f3
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Date deposited: 15 Mar 2021 17:31
Last modified: 17 Mar 2024 06:23
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Contributors
Author:
Christopher E. Elgar
Author:
Haleema Y. Otaif
Author:
Xue Zhang
Author:
Jianzhang Zhao
Author:
Peter Horton
Author:
Joseph M. Beames
Author:
Simon J.A. Pope
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