Second-order superatoms: Au-PAP featuring a three-dimensional cluster-of-clusters core.

The recent characterization of Au-PAP cluster can be viewed as a three-dimensional arrangement featuring four Au motifs. As a result, a new set of superatomic orbitals are built up from the superatomic shell of each constituent unit, denoted by 1S'1P'2S'1D'2P'1F' and, thus, referred to as a second-order superatomic shell structure. This favors the rationalization of larger species toward the formation of cluster-assembled materials of different sizes.