Exploring the electronic properties and cation complexation of polyoxoaurates [Au(III)4X4Om](n-) (X = Si(IV), P(V), Ge(IV), As(V), and Se(IV)) using quantum chemical calculations.

Quantum chemical calculations were performed to explore the structural and electronic properties of the two polyoxoaurates, [Au(III)4As(V)4O20](8-) (Au4As4) and [Au(III)4Se(IV)4O16](4-) (Au4Se4), known to date, and a number of hypothetical polyoxoaurate derivatives comprising heteroatoms different from arsenic and selenium (namely, Si, Ge and P). In addition, the interactions of [Au(III)4X4Om](n-) (X = As, Se) with alkali-metal cations (Li(+), Na(+), K(+) and Rb(+)) are also analysed. The studies suggest that the geometry structure, electronic properties and nucleophilicity of oxygen atoms of these polyoxoaurates are tuned by the size or electronegativity of the heteroatoms (Si, Ge, P, As and Se). Then, the geometry of [Au(III)4X4Om](n-) (X = As and Se) coordinating with alkali cations from Li(+) to Rb(+) and the complexation energy between [Au(III)4X4Om](n-) and alkali cations were compared. The results show that the stability and electronic structure of heteropolyoxoaurates depend on the entrapped cations. On the basis of the complexation energy, it can be concluded that the ion-pairing effect in arsenate-capped oxoaurate is stronger than that in selenite-capped oxoaurate. These heteropolyoxoaurates are expected to play a role in aqueous behaviour, self-assembly characteristics of polyoxoaurates, ion recognition, selectivity studies and may exhibit potential guest-switchable redox properties.