Li Tian-Yi, Shlian Daniel G, Djurovich Peter I, Thompson Mark E
Department of Chemistry, University of Southern California, Los Angeles, California, 90089, USA.
Department of Chemistry, Columbia University, New York, 10027, USA.
Chemistry. 2021 Apr 7;27(20):6191-6197. doi: 10.1002/chem.202100512. Epub 2021 Mar 5.
A luminescent bimetallic Au complex comprised of N-heterocyclic carbene (NHC) and carbazole (Cz) ligands, that is, (NHC')Au(NHC)AuCz has been synthesized and studied. Both carbene ligands in the bimetallic complex act as electron acceptors in tandem to increase the energy separation between the ground and excited state, which is higher than those found in either monometallic analogue, (NHC)AuCz and (NHC')AuCz. A coplanar geometry designed into the tandem complex ensures sufficient electronic coupling between the π-orbitals of the ligands to impart a strong oscillator strength to the singlet intra-ligand charge-transfer ( ICT) transition. Theoretical modelling indicates that the emissive ICT excited state involves both NHC ligands. The tandem complex gives blue luminescence (λ =480 nm) with a high photoluminescent quantum yield (Φ =0.80) with a short decay lifetime (τ=0.52 μs). Temperature-dependent photophysical studies indicate that emission is via thermally assisted delayed fluorescence (TADF) and give a small singlet-triplet energy difference (ΔE =50 meV, 400 cm ) consistent with the short TADF lifetime.
一种由氮杂环卡宾（NHC）和咔唑（Cz）配体组成的发光双金属金配合物，即（NHC'）Au（NHC）AuCz已被合成并研究。双金属配合物中的两个卡宾配体串联充当电子受体，以增加基态和激发态之间的能量间隔，该能量间隔高于在单金属类似物（NHC）AuCz和（NHC'）AuCz中发现的能量间隔。设计到串联配合物中的共面几何结构确保了配体的π轨道之间有足够的电子耦合，从而赋予单重态配体内电荷转移（ICT）跃迁很强的振子强度。理论建模表明，发光的ICT激发态涉及两个NHC配体。该串联配合物发出蓝色荧光（λ = 480 nm），具有高光致发光量子产率（Φ = 0.80）和短衰减寿命（τ = 0.52 μs）。温度依赖的光物理研究表明，发射是通过热激活延迟荧光（TADF）进行的，并且具有小的单重态-三重态能量差（ΔE = 50 meV，400 cm），这与短的TADF寿命一致。
