Improvements in the Ligand-Exchange Reactivity of Phenylethanethiolate-Protected Au 25 Nanocluster by Ag or Cu Incorporation

This study reports improvements in the ligand-exchange reactivity of phenylethanethiolate-protected Au 25 cluster (Au 25 (SC 2 H 4 Ph) 18 ) following Ag or Cu incorporation. Following the synthesis of Au 25– x M x (SC 2 H 4 Ph) 18 (M = Au, Ag, Cu, or Pd), we determined the ligand-exchange reaction rates, using octanethiol (C 8 H 17 SH) as the exchange ligand, by employing mass spectrometry. The results show that incorporating Ag and Cu enhances the ligand-exchange reactivity of the clusters. On the basis of density functional theory calculations, it is concluded that the elevated reactivity of Au 25– x M x (SC 2 H 4 Ph) 18 (M = Ag or Cu) results from the more highly positive charge density of metal atoms in the staple upon Ag or Cu substitution. In addition, in the presence of Au 25– x M x (SC 2 H 4 Ph) 18 (M = Ag or Cu; x ≠ 0), an improvement in the ligand-exchange reaction rate was also observed for Au 25 (SC 2 H 4 Ph) 18, even though this cluster does not include a heteroatom. This unexpected behavior is attributed to the contribution of a chemical reaction between clusters. These findings are expected to deepen our understanding of ligand-exchange reactions, and lead to design guidelines for the creation of Au n (SR) m clusters exhibiting new chemical compositions and functions, using this reaction.