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

The complexes [Cu­(I)­(POP)­(dmbpy)]­[BF₄] (<b>1</b>) and [Cu­(I)­(POP)­(tmbpy)]­[BF₄] (<b>2</b>) (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 <b>2</b> in a rigid matrix (powder), substantially higher than for <b>1</b> of around 9% under the same conditions. Importantly, it was found that the emission of <b>2</b> 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 <b>1</b> and <b>2</b> 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, <b>2</b> appeared limited to this range, whereas <b>1</b> 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

Luminescent, Enantiopure, Phenylatopyridine Iridium-Based Coordination Capsules

The first molecular capsule based on an [Ir­(ppy)₂]⁺ unit (ppy = 2-phenylatopyridine) has been prepared. Following the development of a method to resolve <i>rac</i>-[(Ir­(ppy)₂Cl)₂] into its enantiopure forms, homochiral Ir₆L₄ octahedra where obtained with the tritopic 1,3,5-tricyanobenzene. Solution studies and X-ray diffraction show that these capsules encapsulate four of the six associated counteranions and that these can be exchanged for other anionic guests. Initial photophysical studies have shown that an ensemble of weakly coordinating ligands can lead to luminescence not present in comparable mononuclear systems

Luminescent, Enantiopure, Phenylatopyridine Iridium-Based Coordination Capsules

The first molecular capsule based on an [Ir­(ppy)₂]⁺ unit (ppy = 2-phenylatopyridine) has been prepared. Following the development of a method to resolve <i>rac</i>-[(Ir­(ppy)₂Cl)₂] into its enantiopure forms, homochiral Ir₆L₄ octahedra where obtained with the tritopic 1,3,5-tricyanobenzene. Solution studies and X-ray diffraction show that these capsules encapsulate four of the six associated counteranions and that these can be exchanged for other anionic guests. Initial photophysical studies have shown that an ensemble of weakly coordinating ligands can lead to luminescence not present in comparable mononuclear systems

Luminescent, Enantiopure, Phenylatopyridine Iridium-Based Coordination Capsules

The first molecular capsule based on an [Ir­(ppy)₂]⁺ unit (ppy = 2-phenylatopyridine) has been prepared. Following the development of a method to resolve <i>rac</i>-[(Ir­(ppy)₂Cl)₂] into its enantiopure forms, homochiral Ir₆L₄ octahedra where obtained with the tritopic 1,3,5-tricyanobenzene. Solution studies and X-ray diffraction show that these capsules encapsulate four of the six associated counteranions and that these can be exchanged for other anionic guests. Initial photophysical studies have shown that an ensemble of weakly coordinating ligands can lead to luminescence not present in comparable mononuclear systems