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Luminescent Gold(III) Thiolates: Supramolecular Interactions Trigger and Control Switchable Photoemissions from Bimolecular Excited States
Author(s) -
Currie Lucy,
FernandezCestau Julio,
Rocchigiani Luca,
Bertrand Benoît,
Lancaster Simon J.,
Hughes David L.,
Duckworth Helen,
Jones Saul T. E.,
Credgington Dan,
Penfold Thomas J.,
Bochmann Manfred
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201603841
Subject(s) - pyrazine , chemistry , supramolecular chemistry , stacking , intermolecular force , crystallography , ligand (biochemistry) , excited state , luminescence , crystal structure , molecule , photoluminescence , dimer , intramolecular force , pi interaction , stereochemistry , photochemistry , organic chemistry , materials science , biochemistry , nuclear physics , receptor , physics , optoelectronics
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 t C 6 H 4 )pyrazine dianion and R=Ph ( 1 ), C 6 H 4 t Bu‐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 3 IL(C^N^C) triplet emissions. By contrast, the unstructured red emissions correlate mainly with a 3 LLCT(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.