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

In this study, we successfully synthesized the rod-like [Au-25(PPh3)(10)(SePh)(5)Cl-2](q) (q = +1 or +2) nanoclusters through kinetic control. The single crystal X-ray crystallography determined their formulas to be [Au-25(PPh3)(10)(SePh)(5)Cl-2](SbF6) and [Au-25(PPh3)(10)(SePh)(5)Cl-2](SbF6)(BPh4), respectively. Compared to the previously reported Au-25 coprotected by phosphine and thiolate ligands (i.e., [Au-25(PPh3)(10)(SR)(5)Cl-2](2+)), the two new rod-like Au-25 nanoclusters show some interesting structural differences. Nonetheless, each of these three nanoclusters possesses two icosahedral Au-13 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 Au-25 nanoclusters; and the changes are different from the previously reported superatom Au-25 nanoclusters. Theoretical calculations indicate that the extra electron results in the half occupation of the highest occupied molecular orbitals in the rod-like Au-25(+) nanoclusters and, thus, significantly affects the electronic structure of the non-superatom Au-25 nanoclusters. This work offers new insights into the relationship between the properties and the valence of the non-superatom gold nanoclusters.