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

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• 作者：Lucy Currie ; Dr. Julio Fernandez-Cestau ; Dr. Luca Rocchigiani ; Dr. Benoî ; t Bertrand ; Prof. Simon J. Lancaster ; Dr. David L. Hughes ; Helen Duckworth ; Saul T. E. Jones ; Dr. Dan Credgington ; Dr. Thomas J. Penfold and Prof. Manfred Bochmann
• 刊名：Chemistry - A European Journal
• 出版年：2017
• 出版时间：January 1, 2017
• 年：2017
• 卷：23
• 期：1
• 页码：105-113
• 全文大小：4647K
• ISSN：1521-3765

文摘

A new family of cyclometallated gold(III) thiolato complexes based on pyrazine-centred pincer ligands has been prepared, (C^N^pz^C)AuSR, where C^N^pz^C=2,6-bis(4-Bu^tC₆H₄)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^N^pz^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.