Doping Effect on the Magnetism of Thiolate-Capped 25-Atom Alloy Nanoclusters

The magnetism of metal nanoclusters (NCs) with discrete electronic structures differs from that of metallic-state nanoparticles. Among the gold NCs, magnetic ones are rare. While 7e [Au25(SR)18]0 (SR = thiolate) was an earlier reported one to be magnetic, its spin properties are yet to be understood. Here, we report the silver-doping effect on the magnetic properties of a series of [Au25–xAgx(SR)18]0 with x ranging from 1 to maximum 9 through analysis by electron paramagnetic resonance (EPR) spectroscopy. This series of M25 (M = Au/Ag) NCs reveals a linear decrease in axial splitting with increasing Ag doping owing to smaller spin–orbit coupling for Ag in comparison to Au, and X-ray crystallography analysis reveals the sites for Ag doping, which provides a basis for understanding the spin properties. The influence of aromatic vs nonaromatic ligands on the EPR signals has also been compared. The electronic structures of M25 NCs have been computed. Overall, this work demonstrates an effective strategy to manipulate the spin properties of NCs by atomically controlled Ag doping.