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

作者：Currie Lucy; Fernandez Cestau Julio; Rocchigiani Luca; Bertrand Benoit; Lancaster Simon J; Hughes David L; Duckworth Helen; Jones Saul T E; Credgington Dan; Penfold Thomas J; Bochmann Manfred

来源：Chemistry - A European Journal, 2017, 23(1): 105-113.

DOI：10.1002/chem.201603841

• coordination chemistry
• gold
• photoluminescence
• stacking interactions
• supramolecular assembly
• tridentate ligands

A new family of cyclometallated gold(III) thiolato complexes based on pyrazine-centred pincer ligands has been prepared, (C(boolean AND)Npz(boolean AND)C)AuSR, where C(boolean AND)Npz(boolean AND)C=2,6-bis(4-(BuC6H4)-C-t)pyrazine dianion and R= Ph (1), C(6)H(4)tBu-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 angstrom) intermolecular pyrazine...pyrazine pi-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 pi-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 (IL)-I-3((CNC)-N-boolean AND-C-boolean AND) triplet emissions. By contrast, the unstructured red emissions correlate mainly with a (LLCT)-L-3(SR ->{((CNC)-N-boolean AND-C-pz boolean AND)(2)}) charge transfer transition from the thiolate ligand to the pi center dot center dot center dot pi dimerized pyrazine. Unusually, the pi-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.

• 出版日期2017-1-1