On the halide aggregation into the [Au4(PPh3)4]4+ cluster core. Insights from structural, optical and interaction energy analysis in [(Ph3PAu)4X2]2+ and [(Ph3PAu)4X]3+ species (X = Cl−, Br−, I−)

Abstract

The aggregation of halide atoms into gold clusters offers an interesting scenario for the development of novel metal-based cavities for anion recognition and sensing applications. Thus, further understanding of the different contributing terms leading to efficient cluster–halide aggregation is relevant to guide their synthetic design. In this report, we evaluate the formation of [(Ph₃PAu)₄X₂]²⁺ and [(Ph₃PAu)₄X]³⁺ species (X = Cl⁻, Br⁻, I⁻) in terms of different energy contributions underlying the stabilization of the cluster–halide interaction, and the expected UV-vis absorption profiles as a result of the variation in frontier orbital arrangements. Our results denote that a non-planar Au₄ core shape enables enhanced halide aggregation, which is similar for Cl⁻, Br⁻, and I⁻, in comparison to the hypothetical planar Au₄ counterparts. The electrostatic nature of the interaction involves a decreasing ion–dipole term along with the series, and for iodine species, higher-order electrostatic contributions become more relevant. Hence, the obtained results help in gaining further understanding of the different stabilizing and destabilizing contributions to suitable cluster-based cavities for the incorporation of different monoatomic anions.