How a Single Electron Affects the Properties of the “Non-Superatom” Au25 Nanoclusters

In this study, we successfully synthesized the rod-like [Au25(PPh3)10(SePh)5Cl2]q (q = +1 or +2) nanoclusters through kinetic control. The single crystal X-ray crystallography determined their formulas to be [Au25(PPh3)10(SePh)5Cl2]­(SbF6) and [Au25(PPh3)10(SePh)5Cl2]­(SbF6)­(BPh4), respectively. Compared to the previously reported Au25 coprotected by phosphine and thiolate ligands (i.e., [Au25(PPh3)10(SR)5Cl2]2+), the two new rod-like Au25 nanoclusters show some interesting structural differences. Nonetheless, each of these three nanoclusters possesses two icosahedral Au13 units (sharing a vertex gold atom) and the bridging “Au–Se­(S)–Au” motifs. The compositions of the two new nanoclusters were characterized with ESI-MS and TGA. The optical properties, electrochemistry, and magnetism were studied by EPR, NMR, and SQUID. All these results demonstrate that the valence character significantly affects the properties of the “non-superatom” Au25 nanoclusters, and the changes are different from the previously reported “superatom” Au25 nanoclusters. Theoretical calculations indicate that the extra electron results in the half occupation of the highest occupied molecular orbitals in the rod-like Au25+ nanoclusters and, thus, significantly affects the electronic structure of the “non-superatom” Au25 nanoclusters. This work offers new insights into the relationship between the properties and the valence of the “non-superatom” gold nanoclusters.