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Luminescent Gold(III) Thiolates: Supramolecular Interactions Trigger and Control Switchable Photoemissions from Bimolecular Excited States

Lookup NU author(s): Dr Thomas Penfold

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by Wiley, 2017.

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Abstract

A new family of cyclometallated gold(III) thiolato complexes based on pyrazine-centred pincer ligands has been prepared, (C^Npz^C)AuSR, where C^Npz^C=2,6-bis(4-ButC6H4)pyrazine dianion and R=Ph (1), C6H4tBu-4 (2), 2-pyridyl (3), 1-naphthyl (1-Np, 4), 2-Np (5), quinolinyl (Quin, 6), 4-methylcoumarinyl (Coum, 7) and 1-adamantyl (8). The complexes were isolated as yellow to red solids in high yields using mild synthetic conditions. The single-crystal X-ray structures revealed that the colour of the deep-red solids is associated with the formation of a particular type of short (3.2–3.3 Å) intermolecular pyrazine⋅⋅⋅pyrazine π-interactions. In some cases, yellow and red crystal polymorphs were formed; only the latter were emissive at room temperature. Combined NMR and UV/Vis techniques showed that the supramolecular π-stacking interactions persist in solution and give rise to intense deep-red photoluminescence. Monomeric molecules show vibronically structured green emissions at low temperature, assigned to ligand-based 3IL(C^N^C) triplet emissions. By contrast, the unstructured red emissions correlate mainly with a 3LLCT(SR→{(C^Npz^C)2}) charge transfer transition from the thiolate ligand to the π⋅⋅⋅π dimerized pyrazine. Unusually, the π-interactions can be influenced by sample treatment in solution, such that the emissions can switch reversibly from red to green. To our knowledge this is the first report of aggregation-enhanced emission in gold(III) chemistry.


Publication metadata

Author(s): Currie L, Fernandez-Cestau J, Rocchigiani L, Bertrand B, Lancaster SJ, Hughes DL, Duckworth H, Jones STE, Credgington D, Penfold TJ, Bochmann M

Publication type: Article

Publication status: Published

Journal: Chemistry - A European Journal

Year: 2017

Volume: 23

Issue: 1

Pages: 105-113

Print publication date: 01/01/2017

Online publication date: 09/11/2016

Acceptance date: 11/10/2016

ISSN (print): 0947-6539

ISSN (electronic): 1521-3765

Publisher: Wiley

URL: http://dx.doi.org/10.1002/chem.201603841

DOI: 10.1002/chem.201603841


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