Energy upconversion using platinum(II)-BPI photosensitizers

Payce, Ellie N., Wang, Dantong, Zhao, Jianzhang, Horton, Peter N., Coles, Simon J., Platts, James A. ORCID: https://orcid.org/0000-0002-1008-6595 and Pope, Simon J. A. ORCID: https://orcid.org/0000-0001-9110-9711 2025. Energy upconversion using platinum(II)-BPI photosensitizers. Inorganic Chemistry 10.1021/acs.inorgchem.5c04677

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Abstract

Five heteroleptic Pt(II) complexes structurally defined by a diethyl-substituted bis(2-pyridylimino)isoindoline (BPIEt) core and an ancillary alkynyl coligand are reported. Structural variation across Pt(BPIEt)(1–5) was achieved through different alkyne coligands: phenylacetylene (1), 4-ethynylanisole (2), 3-ethynylthiophene (3), 1-ethynyl-4-fluorobenzene (4), 1-ethynyl-4-dimethylaniline (5). Complexes were fully characterized using a range of spectroscopic and analytical techniques: 1H and 13C NMR, IR, UV–vis, luminescence, and transient absorption spectroscopies, HRMS, and cyclic voltammetry. Two X-ray structures revealed a subtle deviation from idealized square planar geometry where the Pt atom lies within the plane defined by the three nitrogen donors of BPIEt. The redox behavior of the complexes showed one irreversible oxidation between +0.61 and +0.82 V (attributed to Pt2+/3+ couple) and two well-defined ligand-based reductions with fully or quasi-reversible character between −1.70 and −2.09 V. Photophysical studies and supporting DFT calculations describe the phosphorescent nature of the complexes (λem = 625–644 nm in toluene) with strong metal-to-ligand charge transfer (MLCT) character and notable singlet oxygen photogeneration (up to 73%). Triplet–triplet annihilation energy upconversion (TTA-UC) investigations in toluene indicated that this class of triplet emitting complex are viable photosensitizers with an impressive maximum efficiency of ΦUC = 29.6% for Pt(BPIEt)(4).

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Chemistry
Publisher:	American Chemical Society
ISSN:	0020-1669
Date of First Compliant Deposit:	15 December 2025
Date of Acceptance:	5 December 2025
Last Modified:	15 Dec 2025 10:45
URI:	https://orca.cardiff.ac.uk/id/eprint/183184

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