Templated atom-precise galvanic synthesis and structure elucidation of a [Ag₂₄Au(SR)₁₈]^- nanocluster

Synthesis of atom-precise alloy nanoclusters with uniform composition is challenging when the alloying atoms are similar in size (for example, Ag and Au). A galvanic exchange strategy has been devised to produce a compositionally uniform [Ag₂₄Au(SR)₁₈]^- cluster (SR: thiolate) using a pure [Ag₂₅(SR)₁₈]^- cluster as a template. Conversely, the direct synthesis of Ag₂₄Au cluster leads to a mixture of [Ag_25-xAu_x(SR)₁₈]^-, x=1-8. Mass spectrometry and crystallography of [Ag₂₄Au(SR)₁₈]^- reveal the presence of the Au heteroatom at the Ag₂₅ center, forming Ag₂₄Au. The successful exchange of the central Ag of Ag₂₅ with Au causes perturbations in the Ag₂₅ crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag₂₅ and Ag₂₄Pd clusters with same ligand and structural framework, providing new insights into the modulation of cluster properties with dopants at the single-atom level. A [Ag₂₄Au(SR)₁₈]^- nanocluster was synthesized by a galvanic exchange strategy and characterized using mass spectrometry and single-crystal XRD. The replacement of the central Ag atom of Ag₂₅(SR)₁₈ by Au occurs without compromising Ag₂₅ integrity. Subtle changes in the Ag₂₅ structural framework after doping caused significant changes in the stability, electronic, optical, and luminescence properties relative to the properties of the parent Ag₂₅.