Thermally Activated Delayed Fluorescence (TADF) and Enhancing Photoluminescence Quantum Yields of [Cu(diimine)(diphosphine)]+ Complexes—Photophysical, Structural, and Computational Studies

Charlotte L. Linfoot, Markus J. Leitl, Patricia Richardson, Andreas F. Rausch, Oleg Chepelin, Fraser J. White, Hartmut Yersin, Neil Robertson

Research output: Contribution to journalArticlepeer-review

Abstract

The complexes [Cu(I)(POP)(dmbpy)][BF4] (1) and [Cu(I)(POP)(tmbpy)][BF4] (2) (dmbpy = 4,4′-dimethyl-2,2′-bipyridyl; tmbpy = 4,4′,6,6′-tetramethyl-2,2′-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 ±10° 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.
Original languageEnglish
Pages (from-to)10854–10861
JournalInorganic Chemistry
Volume53
Issue number20
Early online date23 Jul 2014
DOIs
Publication statusPublished - 20 Oct 2014

Fingerprint Dive into the research topics of 'Thermally Activated Delayed Fluorescence (TADF) and Enhancing Photoluminescence Quantum Yields of [Cu<sup>I </sup>(diimine)(diphosphine)]<sup>+</sup> Complexes—Photophysical, Structural, and Computational Studies'. Together they form a unique fingerprint.

Cite this