Luminescent gold(III) thiolates: Supramolecular interactions trigger and control switchable photoemissions from bimolecular excited states

Currie, Lucy, Fernandez-Cestau, Julio, Rocchigiani, Luca, Bertrand, Benoît, Lancaster, Simon J., Hughes, David L., Duckworth, Helen, Jones, Saul T. E., Credgington, Dan, Penfold, Thomas J. and Bochmann, Manfred (2017) Luminescent gold(III) thiolates: Supramolecular interactions trigger and control switchable photoemissions from bimolecular excited states. Chemistry - A European Journal, 23 (1). 105–113. ISSN 0947-6539

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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.

Item Type: Article
Additional Information: © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Uncontrolled Keywords: coordination chemistry,gold,photoluminescence,stacking interactions,supramolecular assembly,tridentate ligands
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: Pure Connector
Date Deposited: 27 Sep 2016 12:00
Last Modified: 19 Sep 2019 00:10
URI: https://ueaeprints.uea.ac.uk/id/eprint/60619
DOI: 10.1002/chem.201603841

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