Emission properties and Cu(i)–Cu(i) interaction in 2-coordinate dicopper(i)-bis(N-heterocyclic)carbene complexes

Abstract

The synthesis, characterization, and emission properties of 2-coordinate dicopper(i) complexes bearing two trimethylene-bridged bis-NHC ligands, [Cu2(L3Me)2](PF6)2 (1), [Cu2(L3Et)2](PF6)2 (2), [Cu2(L3Bu)2](PF6)2 (3), [Cu2(L3MeOPh)2](PF6)2 (4) and [Cu2(L3Mes)2](PF6)2 (5), where L3R denotes trimethylene-bridged bis(N-heterocyclic)carbene (NHC) ligand substituted by two R groups at the nitrogen atoms of NHC, have been investigated. The quantum yield, Φ, and the lifetime, τ, of the emission of 2, are 0.21 and 25 μs, respectively in methanol, which is a well-known solvent for quenching the luminescence of many copper(i) complexes. The 8-shaped geometry of the dicopper(i) complexes brings a considerable copper(i)-copper(i) interaction which affects the luminescent properties. Additionally, we find that methoxyphenyl and mesityl groups substituted at the nitrogen atom of the NHC moiety drastically stabilize the bis(NHC) copper(i) complexes even in air-saturated acetone-d6.

Triboluminescence of a new family of CuI–NHC complexes in crystalline solid and in amorphous polymer films

“…For comparison, the air stability of some previously reported NHC Cu I complexes in the crystal state has been reported to vary greatly depending on the ligand structure and sterics-inuencing substituents, [27][28][29] while air stability in solution is usually limited to several hours in most cases. [27][28][29][30][31][32] Bulkier Dipp-substituted NHC ligand containing complex 2 shows higher PLQY both in the solid state (Table 1) and in solution (Table S1 †) compared to the less bulky mesitylsubstituted NHC containing complex 1 with otherwise the same Me-substituted pyridinophane ligand. This could be due to more efficient suppression of non-radiative decay in the presence of a bulky Dipp-substituent, consistent with a smaller non-radiative decay rate constant for complex 1 compared to complex 2 (Table S2 †).…”

Synthesis, Structures, and Photophysical Properties of Novel Four-Coordinate Cu(I) Complexes Supported by Chelating N-Heterocyclic Carbene Ligands

“…It is well known that N-heterocyclic carbenes (NHCs) are excellent ligands for transition metal complexes because of their strong σ-donating ability and modest π-accepting ability. Moreover, it has been proven that two- and three-coordinate Cu(I) complexes supported by NHC ligands can give efficient TADF or phosphorescence (Krylova et al, 2012; Leitl et al, 2014; Marion et al, 2014; Elie et al, 2016; Nishikawa et al, 2016; Hamze et al, 2017; Lu et al, 2018). In view of these findings, we synthesized several four-coordinate Cu(I)-NHC complexes with efficient TADF by replacing the diimine ligands in Cu(P ∧ P)(N ∧ N)] + with the chelating NHC ligands consisting of imidazolylidene and pyridine (Wang et al, 2016, 2018), and the Zhao group also carried out similar research (Liu et al, 2017; Wang J. et al, 2017; Xu et al, 2018).…”

Dinuclear N-heterocyclic carbene copper(I) complexes

“…Recently, this family of complexes was further extended by Tsubomura and co-workers (Scheme 30) [60]. The copper complexes were again accessed via transmetallation from the corresponding silver species.…”

“…Library of propylene-linked copper(I)-bis(NHC) complexes 62-65 and their molecular structure determined by X-ray diffraction. Solvent molecules and H atoms are omitted for clarity [60].…”