Exploring the electronic properties and cation complexation of polyoxoaurates [AuIII4X4Om]n− (X = SiIV, PV, GeIV, AsV, and SeIV) using quantum chemical calculations

Abstract

Quantum chemical calculations were performed to explore the structural and electronic properties of the two polyoxoaurates, [Au^III₄As^V₄O₂₀]⁸⁻ (Au₄As₄) and [Au^III₄Se^IV₄O₁₆]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^III₄X₄O_m]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^III₄X₄O_m]ⁿ⁻ (X = As and Se) coordinating with alkali cations from Li⁺ to Rb⁺ and the complexation energy between [Au^III₄X₄O_m]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.