Conversion of anionic [Au25(SCH2CH2Ph)18]- cluster to charge neutral cluster via air oxidation

We report a solution-phase conversion process of the [Au-25(SCH2CH2Ph)(18)](-) anionic cluster into a charge neutral cluster [Au-25(SCH2CH2Ph)(18)](0) via air oxidation. The one-electron loss of the Au-25(-) cluster and conversion to Au-25(0) is a surprise in light of the chemical inertness of gold nanoparticles. In contrast with the crystal structure of the anion Cluster Au-25(-), which exhibits apparent structural distortions in the Au25S18 framework, such distortions are not observed in the neutral cluster. The cluster charge effect is also manifested in the optical absorption spectra of the clusters. Given the only recently reported structure of the parent Au-25(-) cluster, it is of substantial interest whether its one-electron oxidized product is similar to that of Au-25(-). This work unambiguously determined the structure of the one-electron oxidized product and correlates the structure with the optical properties.