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 [Ag-25(SR)(18)](-) cluster as a template. Conversely, the direct synthesis of Ag24Au cluster leads to a mixture of [Ag25-xAux(SR)(18)](-), x=1-8. Mass spectrometry and crystallography of [Ag24Au(SR)(18)](-) reveal the presence of the Au heteroatom at the Ag-25 center, forming Ag24Au. The successful exchange of the central Ag of Ag-25 with Au causes perturbations in the Ag-25 crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag-25 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.