The electrooxidation-induced structural changes of gold di-superatomic molecules: Au23vs. Au25

Abstract

The gold cluster compounds Au₃₈(SC₂H₄Ph)₂₄ and [Au₂₅(PPh₃)₁₀(SC₂H₄Ph)₅Cl₂]²⁺ are known to possess bi-icosahedral Au₂₃ and Au₂₅ cores, respectively, inside their ligand shells. These Au cores can be viewed as quasi-molecules composed of two Au₁₃ superatoms sharing three and one Au⁺ atoms, respectively. In the present work, we studied the structural changes of these gold di-superatomic molecules upon electrooxidation via spectroelectrochemical techniques, X-ray absorption fine structure analysis, and density functional theory calculations. The Au₂₃ core was electrochemically stable, but the Au₂₅ core underwent irreversible structural change. This marked difference in the stability of the oxidized states is ascribed to differences in the bonding scheme of Au₁₃ units and/or the bonding nature of the protecting ligands.