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

Abstract

<p>The gold cluster compounds Au<sub>38</sub>(SC<sub>2</sub>H<sub>4</sub>Ph)<sub>24</sub> and [Au<sub>25</sub>(PPh<sub>3</sub>)<sub>10</sub>(SC<sub>2</sub>H<sub>4</sub>Ph)<sub>5</sub>Cl<sub>2</sub>]<sup>2+</sup> are known to possess bi-icosahedral Au<sub>23</sub> and Au<sub>25</sub> cores, respectively, inside their ligand shells. These Au cores can be viewed as quasi-molecules composed of two Au<sub>13</sub> superatoms sharing three and one Au<sup>+</sup> 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<sub>23</sub> core was electrochemically stable, but the Au<sub>25</sub> 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<sub>13</sub> units and/or the bonding nature of the protecting ligands.</p>