A new class of luminescent Cu(<scp>i</scp>) complexes with tripodal ligands – TADF emitters for the yellow to red color range

Gneuß, Timo; Leitl, Markus J.; Finger, Lars H.; Rau, N.; Yersin, Hartmut; Sundermeyer, Jörg

doi:10.1039/c4dt02631d

Cited by 88 publications

(77 citation statements)

References 108 publications

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“…The individual value depends on molecular properties, for example, on the extent of SOC of higher lying singlets to the lowest triplet state, but also on the local environment, such as a fluid or a rigid matrix . In general, a significant prompt fluorescence (S 1 →S 0 ) is not detected, but a very bright long‐lived phosphorescence (T 1 →S 0 ) is frequently observed at low temperature . At higher temperature and in a situation of a fast thermal equilibration, population of the higher lying singlet state is governed by the Boltzmann distribution.…”

Section: Tadf Molecular Parameters and Diversity Of Materialsmentioning

confidence: 99%

TADF Material Design: Photophysical Background and Case Studies Focusing on Cu^Iand Ag^IComplexes

et al. 2017

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The development of organic light emitting diodes (OLEDs) and the use of emitting molecules have strongly stimulated scientific research of emitting compounds. In particular, for OLEDs it is required to harvest all singlet and triplet excitons that are generated in the emission layer. This can be achieved using the so-called triplet harvesting mechanism. However, the materials to be applied are based on high-cost rare metals and therefore, it has been proposed already more than one decade ago by our group to use the effect of thermally activated delayed fluorescence (TADF) to harvest all generated excitons in the lowest excited singlet state S . In this situation, the resulting emission is an S →S fluorescence, though a delayed one. Hence, this mechanism represents the singlet harvesting mechanism. Using this effect, high-cost and strong SOC-carrying rare metals are not required. This mechanism can very effectively be realized by use of Cu or Ag complexes and even by purely organic molecules. In this investigation, we focus on photoluminescence properties and on crucial requirements for designing Cu and Ag materials that exhibit short TADF decay times at high emission quantum yields. The decay times should be as short as possible to minimize non-radiative quenching and, in particular, chemical reactions that frequently occur in the excited state. Thus, a short TADF decay time can strongly increase the material's long-term stability. Here, we study crucial parameters and analyze their impact on the TADF decay time. For example, the energy separation ΔE(S -T ) between the lowest excited singlet state S and the triplet state T should be small. Accordingly, we present detailed photophysical properties of two case-study materials designed to exhibit a large ΔE(S -T ) value of 1000 cm (120 meV) and, for comparison, a small one of 370 cm (46 meV). From these studies-extended by investigations of many other Cu TADF compounds-we can conclude that just small ΔE(S -T ) is not a sufficient requirement for short TADF decay times. High allowedness of the transition from the emitting S state to the electronic ground state S , expressed by the radiative rate k (S →S ) or the oscillator strength f(S →S ), is also very important. However, mostly small ΔE(S -T ) is related to small k (S →S ). This relation results from an experimental investigation of a large number of Cu complexes and basic quantum mechanical considerations. As a consequence, a reduction of τ(TADF) to below a few μs might be problematic. However, new materials can be designed for which this disadvantage is not prevailing. A new TADF compound, Ag(dbp)(P -nCB) (with dbp=2,9-di-n-butyl-1,10-phenanthroline and P -nCB=bis-(diphenylphosphine)-nido-carborane) seems to represent such an example. Accordingly, this material shows TADF record properties, such as short TADF decay time at high emission quantum yield. These properties are based (i) on geometry optimizations of the Ag complex for a fast radiative S →S rate and (ii) on restricting the extent of geometry reorganiza...

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Section: Tadf Molecular Parameters and Diversity Of Materialsmentioning

confidence: 99%

TADF Material Design: Photophysical Background and Case Studies Focusing on Cu^Iand Ag^IComplexes

et al. 2017

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“…14,35,36,56,[59][60][61][62] To our knowledge only very few Cu(I) complexes with tripodal ligands have been studied with 15 regard to their photophysical properties. 54 35 prepared in a two-step synthesis. In the first step, the tripodal ligand tris(2-pyridyl)methane (tpym) was prepared according to a literature method (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

A new class of deep-blue emitting Cu(i) compounds – effects of counter ions on the emission behavior

et al. 2015

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Three deep blue emitting Cu(I) compounds, [Cu(PPh3)tpym]PF6, [Cu(PPh3)tpym]BF4, and [Cu(PPh3)tpym]BPh4 (tpym = tris(2-pyridyl)methane, PPh3 = triphenylphosphine) featuring the tripodally coordinating tpym and the monodentate PPh3 ligands were studied with regard to their structural and photophysical properties. The compounds only differ in their respective counter ions which have a strong impact on the emission properties of the powder samples. For example, the emission quantum yield can be significantly increased for the neat material from less than 10% to more than 40% by exchanging BPh4(-) with PF6(-). These effects can be linked to different molecular packings which depend on the counter ion. In agreement with these results, it was found that the emission properties also strongly depend on the surrounding matrix environment which was elucidated by investigating photophysical properties of the compounds as powders, doped into a polymer matrix, and dissolved in a fluid solution, respectively. The observed differences in the emission behavior can be explained by different and pronounced distortions that occur in the excited state. These distortions are also displayed by density functional theory (DFT) calculations.

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“…The unambiguous assignment of NMR resonances (Scheme ) was accomplished by additional 2D NMR experiments ( 1 H– 1 H COSY, 1 H– 1 H NOESY, 1 H– 13 C HMQC, and 1 H‐ 13 C HMBC experiments; see the Supporting Information for details). Li[EtAl(6‐Me‐2‐py) 3 ] ( 1 Li) and [Li{EtAl(OMe)(6‐Me‐2‐py) 2 }] 2 ( 2 b Li) were synthesized as described previously. X‐ray data were collected on a Bruker D8 QUEST diffractometer with an Incoatec IμS Cu microfocus source.…”

Section: Methodsmentioning

confidence: 99%

Postfunctionalization of Tris(pyridyl) Aluminate Ligands: Chirality, Coordination, and Supramolecular Chemistry

García-Romero

Plajer

Álvarez‐Miguel

et al. 2018

Chemistry A European J

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Postfunctionalization of the aluminate anion [EtAl(6-Me-2-py) ] (1) (2-py=2-pyridyl) with alkoxide ligands can be achieved by the selective reactions of the lithium salt 1 Li with alcohols in the appropriate stoichiometry. This method can be used to introduce 3- and 4-py functionality in the form of 3- and 4-alkoxymethylpyridyl groups, while maintaining the integrity of the aluminate framework, thereby giving entry to new supramolecular chemistry. Chirality can be introduced either by using a chiral alcohol as a reactant or by the stepwise reaction of 1 Li with two different nonchiral alcohols. The latter route has allowed the synthesis of a rare example of a chiral-at-aluminium aluminate.

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A new class of luminescent Cu(i) complexes with tripodal ligands – TADF emitters for the yellow to red color range

Cited by 88 publications

References 108 publications

TADF Material Design: Photophysical Background and Case Studies Focusing on Cu^Iand Ag^IComplexes

TADF Material Design: Photophysical Background and Case Studies Focusing on Cu^Iand Ag^IComplexes

A new class of deep-blue emitting Cu(i) compounds – effects of counter ions on the emission behavior

Postfunctionalization of Tris(pyridyl) Aluminate Ligands: Chirality, Coordination, and Supramolecular Chemistry

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A new class of luminescent Cu(i) complexes with tripodal ligands – TADF emitters for the yellow to red color range

Cited by 88 publications

References 108 publications

TADF Material Design: Photophysical Background and Case Studies Focusing on CuIand AgIComplexes

TADF Material Design: Photophysical Background and Case Studies Focusing on CuIand AgIComplexes

A new class of deep-blue emitting Cu(i) compounds – effects of counter ions on the emission behavior

Postfunctionalization of Tris(pyridyl) Aluminate Ligands: Chirality, Coordination, and Supramolecular Chemistry

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TADF Material Design: Photophysical Background and Case Studies Focusing on Cu^Iand Ag^IComplexes

TADF Material Design: Photophysical Background and Case Studies Focusing on Cu^Iand Ag^IComplexes