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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
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
0947-6539
3427-3439
Elgar, Christopher E.
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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.
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), 3427-3439. (doi:10.1002/chem.202004146).

Record type: Article

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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Accepted/In Press date: 26 November 2020
e-pub ahead of print date: 19 January 2021
Published date: 15 February 2021
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
ORCID for Peter Horton: ORCID iD orcid.org/0000-0001-8886-2016
ORCID for Simon J. Coles: ORCID iD orcid.org/0000-0001-8414-9272

Catalogue record

Date deposited: 15 Mar 2021 17:31
Last modified: 26 Nov 2021 06:17

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Contributors

Author: Christopher E. Elgar
Author: Haleema Y. Otaif
Author: Xue Zhang
Author: Jianzhang Zhao
Author: Peter Horton ORCID iD
Author: Simon J. Coles ORCID iD
Author: Joseph M. Beames
Author: Simon J.A. Pope

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