Following the Reactivity of Au25(SC8H9)18- Clusters with Pd2+ and Ag+ Ions Using in Situ X-ray Absorption Spectroscopy: A Tale of Two Metals

This work examines the reaction between Au-25(SC8H9)(18)(-) clusters with palladium acetate (Pd2+) and silver nitrate (Ag+) using UV-vis, transmission electron microscopy (TEM), extended X-ray absorption spectroscopy (EXAFS), and in situ liquid cell X-ray absorption spectroscopy (XAS). UV-vis results show that upon the addition of Pd2+ and Ag+ salts to Au-25(SC8H9)(18)(-) clusters significant changes are seen in the optical properties of the clusters. In the case of Pd, there is little to no change in the size of the clusters evidenced by TEM, while for Ag systems, significant particle growth is seen. In situ XAS results show that Pd2+ reacts with the staple motifs of Au-25(SC8H9)(18)(-) clusters and forms Pd(II) thiolate species, as shown by the Pd L-3- and Au L-3-edge data as well as Pd K-edge EXAFS results. However, Ag L-3-edge data suggest that Ag+ reduces to Ag on the cluster core and does not form Ag(I) thiolate species. This work highlights the power of using in situ XANES to follow Au cluster transformations in liquid environments.