Site Preference in Multimetallic Nanoclusters: Incorporation of Alkali Metal Ions or Copper Atoms into the Alkynyl-Protected Body-Centered Cubic Cluster [Au Ag (C≡C Bu) ]<sup/>.

The synthesis, structure, substitution chemistry, and optical properties of the gold-centered cubic monocationic cluster [Au@Ag @Au (C≡C Bu) ] are reported. The metal framework of this cluster can be described as a fragment of a body-centered cubic (bcc) lattice with the silver and gold atoms occupying the vertices and the body center of the cube, respectively. The incorporation of alkali metal atoms gave rise to [M Ag Au (C≡C Bu) ] clusters (n=1 for M=Na, K, Rb, Cs and n=2 for M=K, Rb), with the alkali metal ion(s) presumably occupying the vertex site(s), whereas the incorporation of copper atoms produced [Cu Ag Au (C≡C Bu) ] clusters (n=1-6), with the Cu atom(s) presumably occupying the capping site(s). The parent cluster exhibited strong emission in the near-IR region (λ =818 nm) with a quantum yield of 2 % upon excitation at λ=482 nm. Its photoluminescence was quenched upon substitution with a Na ion. DFT calculations confirmed the superatom characteristics of the title compound and the sodium-substituted derivatives.