Organometallic platinum(ii) photosensitisers that demonstrate ligand‐modulated triplet‐triplet annihilation energy upconversion efficiencies

Fitzgerald, Sophie A., Xiao, Xiao, Zhao, Jianzhang, Horton, Peter N., Coles, Simon J., Knighton, Richard C., Ward, Benjamin D. ORCID: https://orcid.org/0000-0003-1406-5940 and Pope, Simon J. A. ORCID: https://orcid.org/0000-0001-9110-9711 2022. Organometallic platinum(ii) photosensitisers that demonstrate ligand‐modulated triplet‐triplet annihilation energy upconversion efficiencies. Chemistry - A European Journal , e202203241. 10.1002/chem.202203241

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Abstract

A series of 2‐phenylquinoxaline ligands have been synthesised that introduce either CF3 or OCF3 electron‐withdrawing groups at different positions of the phenyl ring. These ligands were investigated as cyclometalating reagents for platinum(II) to give neutral complexes of the form [Pt(C^N)(acac)] (in which C^N=cyclometalating ligand; acac=acetyl acetonate). X‐ray crystallographic studies on three examples showed that the complexes adopt an approximate square planar geometry. All examples revealed strong Pt−Pt linear contacts of 3.2041(6), 3.2199(3) and 3.2586(2) Å. The highly coloured complexes display efficient visible absorption at 400–500 nm (ϵ ≈5000 M−1 cm−1) and orange red photoluminescent characteristics (λem=603–620 nm; Φem ≤37 %), which were subtly tuned by the ligand. Triplet emitting character was confirmed by microsecond luminescence lifetimes and the photogeneration of singlet oxygen with quantum efficiencies up to 57 %. Each complex was investigated as a photosensitiser for triplet–triplet annihilation energy upconversion using 9,10‐diphenylanthracene as the annihilator species: a range of good upconversion efficiencies (ΦUC 5.9–14.1 %) were observed and shown to be strongly influenced by the ligand structure in each case.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Chemistry
Additional Information:	License information from Publisher: LICENSE 1: URL: http://creativecommons.org/licenses/by-nc/4.0/
Publisher:	Wiley
ISSN:	0947-6539
Date of First Compliant Deposit:	3 January 2023
Date of Acceptance:	17 November 2022
Last Modified:	06 Jan 2024 03:05
URI:	https://orca.cardiff.ac.uk/id/eprint/155328

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