title: Luminescent Gold(III) Thiolates: Supramolecular Interactions Trigger and Control Switchable Photoemissions from Bimolecular Excited States.
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-based3IL(C^N^C) triplet emissions. By contrast, the unstructured red emissions correlate mainly with a3LLCT(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.
authors.affiliation: School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: Lucy
authors.initials: L
authors.lastname: Currie
authors.affiliation: School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: Julio
authors.identifier: 0000-0001-7663-6222
authors.initials: J
authors.lastname: Fernandez-Cestau
authors.affiliation: School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: Luca
authors.identifier: 0000-0002-2679-8407
authors.initials: L
authors.lastname: Rocchigiani
authors.affiliation: School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: Benoît
authors.identifier: 0000-0003-0542-4454
authors.initials: B
authors.lastname: Bertrand
authors.affiliation: School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Lancaster
authors.affiliation: School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: David L
authors.initials: DL
authors.lastname: Hughes
authors.affiliation: School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom.
authors.forename: Helen
authors.initials: H
authors.lastname: Duckworth
authors.affiliation: Department of Physics, Cavendish Laboratory, Cambridge University, Cambridge, CB3 0HF, United Kingdom.
authors.forename: Saul T E
authors.identifier: 0000-0001-6007-2530
authors.initials: ST
authors.lastname: Jones
authors.affiliation: Department of Physics, Cavendish Laboratory, Cambridge University, Cambridge, CB3 0HF, United Kingdom.
authors.forename: Dan
authors.identifier: 0000-0003-4246-2118
authors.initials: D
authors.lastname: Credgington
authors.affiliation: School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Penfold
authors.affiliation: School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: Manfred
authors.identifier: 0000-0001-7736-5428
authors.initials: M
authors.lastname: Bochmann
keywords: coordination chemistry; gold; photoluminescence; stacking interactions; supramolecular assembly; tridentate ligands