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Emissive gold(iii) complexes of pincer 2,6-diphenylpyridines also bearing a phenylacetylide ligand have been modified at both the pincer and phenylacetylide to confer liquid crystalline properties, with most complexes showing a columnar hexagonal phase in the condensed phase. Solution NMR studies show a preferred orientation for self-association, consistent with structural parameters in the liquid crystal phase obtained by X-ray methods. While the pattern of substitution of the phenylacetylide has no discernible effect on the photophysics, when two alkoxy chains are attached to the pincer ligands, photoluminescence quantum yields (PLQY) of around 3% are found, whereas when four alkoxy chains are attached the PLQY increases significantly to 36%. Insight from computational chemistry indicated that the incorporation of the alkoxy donor groups raises the energy of the pincer-based HOMO−1 orbital, with a concomitant lowering of the LUMO ← HOMO−1 transition energy, consistent with an experimentally observed red shift. The gold complexes were fabricated into OLED devices using solution processing methods, being doped into the emissive layer at 5%, leading to external quantum efficiencies of up to 7.14%, values that compare well with those of related complexes in the literature.
Bibliographical noteFunding Information:
We thank the University of York (RRP) and the EPSRC (computational equipment used in this study, grants EP/H011455/1 and EP/K031589/1) for funding, Johnson Matthey for generous loans of gold salts, the Royal Society and the National Natural Science Foundation of China (51911530197, 51773021) for an International Exchange Award (DWB & YW), Rebecca Howarth for the preparation of some precursor ligands and Alice McEllin for recording some cyclic voltammetry data.
© The Royal Society of Chemistry 2021.
Copyright 2021 Elsevier B.V., All rights reserved.
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