Thermally activated delayed fluorescence Au‐Ag‐oxo nanoclusters: From photoluminescence to radioluminescence

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, Au18Ag26(R1COO)12(R2C≡C)24(μ4‐O)2(μ3‐O)2 (Au18Ag26, where R1 = CH3‐, Ph‐, CHOPh‐ or CF3Ph‐; R2 = Ph‐ or FPh‐). These nanoclusters exhibit exceptional TADF properties, including a small S1‐T1 energy gap of 55.5 meV, a high absolute photoluminescence quantum yield of 86.7%, and a microseconds TADF decay time of 1.6 μs at ambient temperature. Meanwhile, Au18Ag26 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 O2−. 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 O2−‐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.

[Au9Ag6(CCR)10(DPPM)2Cl2](PPh4): a four-electron cluster with a bi-decahedral twisted metal core

“…1–6 With the advancement of sophisticated characterization techniques, numerous metal clusters with atomic-level resolved structures have been reported to date. 7–21 It has been observed that the metal core of many of these clusters shares the same polyhedral units, despite variations in peripheral ligands or metal–ligand motif structures. These polyhedral units encompass an M 13 centered icosahedron, 22–28 an M 6 octahedron, 29–35 an M 13 cuboctahedron 36 and an M 7 decahedron, 37–42 among others, where ‘M’ represents Au, Ag, Cu, or other metal atoms or their mixtures.…”

Influence of the substituents of the thiol ligand on the optical properties of AuCu14

“…Luminescent metal clusters have attracted significant interest because of their application in the fields of lighting and sensing, etc. 1–4 However, it is challenging to obtain a high emission efficiency and designable wavelength because metal cluster-based emitters have complex energy level structures and excited state relaxation processes. 5,6 Therefore, the building of the relationship between the structure and optical properties is fundamentally important for designing and synthesizing high luminous performance metal clusters.…”