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 [Au-25(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 M-25 (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 M-25 NCs have been computed. Overall, this work demonstrates an effective strategy to manipulate the spin properties NCs by atomically controlled Ag doping.