Thermally Activated Delayed Fluorescence (TADF) and Enhancing Photoluminescence Quantum Yields of [CuI(diimine)(diphosphine)]+ Complexes鈥擯hotophysical, Structural, and Computatio

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• 作者：Charlotte L. Linfoot ; Markus J. Leitl ; Patricia Richardson ; Andreas F. Rausch ; Oleg Chepelin ; Fraser J. White ; Hartmut Yersin ; Neil Robertson
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：October 20, 2014
• 年：2014
• 卷：53
• 期：20
• 页码：10854-10861
• 全文大小：467K
• ISSN：1520-510X

文摘

The complexes [Cu(I)(POP)(dmbpy)][BF₄] (1) and [Cu(I)(POP)(tmbpy)][BF₄] (2) (dmbpy = 4,4鈥?dimethyl-2,2鈥?bipyridyl; tmbpy = 4,4鈥?6,6鈥?tetramethyl-2,2鈥?bipyridyl; POP = bis[2-(diphenylphosphino)-phenyl]ether) have been studied in a wide temperature range by steady-state and time-resolved emission spectroscopy in fluid solution, frozen solution, and as solid powders. Emission quantum yields of up to 74% were observed for 2 in a rigid matrix (powder), substantially higher than for 1 of around 9% under the same conditions. Importantly, it was found that the emission of 2 at ambient temperature represents a thermally activated delayed fluorescence (TADF) which renders the compound to be a good candidate for singlet harvesting in OLEDs. The role of steric constraints within the complexes, in particular their influences on the emission quantum yields, were investigated by hybrid-DFT calculations for the excited triplet state of 1 and 2 while manipulating the torsion angle between the bipyridyl and POP ligands. Both complexes showed similar flexibility within a 卤10掳 range of the torsion angle; however, 2 appeared limited to this range, whereas 1 could be further twisted with little energy demand. It is concluded that a restricted flexibility leads to a reduction of nonradiative deactivation and thus an increase of emission quantum yield.