Al12Cu Superatom as Stable Building Block of Ionic Salts

The neutral copper aluminum cluster complex Al12CuM3 [M = K, K3O, and K(2,2,2-crypt)] has been investigated at the PBE96 level of theory. It is found that Al12Cu could be considered a superatom mimic of a phosphorus atom. It shows large electron affinity and is able to receive three electrons from elements or compounds with low ionization energies like K, K3O, or K(2,2,2-crypt) to become a stable electronic closed shell with a large gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO gap). Theoretical calculations confirm that similar to the phosphorus atom in PK3, the superatom Al12Cu cluster could form ionic salts, as shown from stable dimers, trimers, and tetramers of the Al12Cu{K(2,2,2-crypt)}(3) complex. On the basis of the maintenance of its integrity in these assemblies it could be predicted that Al12CuM3 holds great potential as a building block for the development of future nanostructured materials. Furthermore, the choice of the K(2,2,2-crypt) molecules to stabilize the salt opens a route to experimentally generate cluster base ionic salts, and we expect that our work motivates experimental investigations of these assemblies.