Extra Silver Atom Triggers Room-Temperature Photoluminescence in Atomically Precise Radarlike Silver Clusters

Luminescent metal clusters show promise for applications in imaging and sensing. However, promoting emission from metal clusters at room temperature is a challenging task owing to the lack of an efficient approach to suppress the nonradiative decay process in metal cores. We report herein that the addition of a silver atom into a metal interstice of the radarlike thiolated silver cluster [Ag₂₇ (S^t Bu)₁₄ (S)₂ (CF₃ COO)₉ (DMAc)₄ ]⋅DMAc (NC1, DMAc=dimethylacetamide), which is non-emissive under ambient conditions, produced another silver cluster [Ag₂₈ (AdmS)₁₄ (S)₂ (CF₃ COO)₁₀ (H₂ O)₄ ] (NC2) that displayed bright green room-temperature photoluminescence aided by the new ligand 1-adamantanethiol (AdmSH). The 28th Ag atom, which hardly affects the geometrical and electronic structures of the Ag-S skeleton, triggered the emission of green light as a result of the rigidity of the cluster structure.