On the Mechanism of Anti-galvanic Metal Displacement Reaction between [Au25(SR)18]- and Metal-Thiolate Complex

Metal displacement reaction is widely used for preparing alloy nanomaterials. In this study, the mechanism of anti-galvanic metal displacement reaction between the atomic precision [Au25(SC2H4Ph)18]- cluster and the metal-thiolate complexes SR-M-SR (M = Ag, Cd, and Hg) is studied based on dispersion correction density functional theory (DFT-D) calculations. The present study reveals that the metal displacement reaction of the Au25 cluster is carried out through two-stage metal diffusion including the rapid diffusion of the metal heteroatom from metal thiolate to the ligand layer of Au25 cluster and then gradual diffusion of the metal heteroatom into the icosahedral 13-atom core. The atomic charge analysis confirms that the SR group plays a crucial role. Due to the partial reducibility of SR group, it can nucleophilic attack Au atom to result in the fracture of the Au-S bond in the ligand layer and the formation of atomic vacancy on the surface of the metal core, which facilitates the metal heteroatom diffusion from the metal-SR complex to the ligand layer of gold cluster and then to the surface of gold core.