SP³-Hybridization Feature of Ag₄ Superatom in Superatomic Molecules

Analogous to atoms, superatoms can be used as building blocks to compose molecules and materials. To demonstrate this idea, the possibility of using tetrahedral Ag₄ cluster to form a series of superatomic molecules Ag₄X₄ (X=H, Li, Na, K, Cu, Ag, Au and F, Cl, Br) is discussed. Based on the super valence bond model, a tetrahedral Ag₄ cluster can be viewed as a 4-electron superatom, which can mimic a sp³ hybridization C atom. By comparison of the representative superatomic molecules Ag₄X₄ (X=Au, Cl) with the corresponding simple molecules CX₄ (X=H, Cl), the similarities in terms of chemical bonding patterns and molecular orbitals (MOs) are conspicuous. Energy calculations predict that the Ag₄ superatom can bind with all the involved ligands. Furthermore, the stabilities of superatomic molecules are enhanced by the large gaps of the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO gaps) and high aromaticity. Our studies may find applications in assembling materials with superatoms.