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Abstract Thermally activated delayed fluorescence (TADF) materials have numerous applications in energy conversion and luminescent imaging. However, they are typically achieved as metal‐organic complexes or pure organic molecules. Herein, we report the largest Au‐Ag‐oxo nanoclusters to date, Au 18 Ag 26 (R 1 COO) 12 (R 2 C≡C) 24 ( μ 4 ‐O) 2 ( μ 3 ‐O) 2 ( Au 18 Ag 26 , where R 1 = CH 3 ‐, Ph‐, CHOPh‐ or CF 3 Ph‐; R 2 = Ph‐ or FPh‐). These nanoclusters exhibit exceptional TADF properties, including a small S 1 ‐T 1 energy gap of 55.5 meV, a high absolute photoluminescence quantum yield of 86.7%, and a microseconds TADF decay time of 1.6 μ s at ambient temperature. Meanwhile, Au 18 Ag 26 shows outstanding stability against oxygen quenching and ambient conditions. Atomic level analysis reveals the strong π⋯π and C‐H⋯π interactions from the aromatic alkynyl ligands and the enhancement of metal‐oxygen‐metal interactions by centrally coordinated O 2− . Modeling of the electronic structure shows spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital, which promote charge transfer from the ligand shell, predominantly carboxylate ligands, to O 2− ‐embedded metal core. Furthermore, TADF Au‐Ag‐oxo nanoclusters exhibit promising radioluminescence properties, which we demonstrate for X‐ray imaging. Our work paves the way for the design of TADF materials based on large metal nanoclusters for light‐emission and radioluminescence applications.
Yuan et al. (Thu,) studied this question.