The electrooxidation-induced structural changes of gold di-superatomic molecules: Au23 vs. Au25

The gold cluster compounds Au-38(SC2H4Ph)(24) and [Au-25(PPh3)(10)(SC2H4Ph)(5)Cl-2](2+) are known to possess bi-icosahedral Au-23 and Au-25 cores, respectively, inside their ligand shells. These Au cores can be viewed as quasi-molecules composed of two Au-13 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 Au-23 core was electrochemically stable, but the Au-25 core underwent irreversible structural change. This marked difference in the stability of the oxidized states is ascribed to differences in the bonding scheme of Au-13 units and/or the bonding nature of the protecting ligands.