DFT Insights into the Variety in the Coordination Modes of the Equatorial Halides in [Au13Ag12(PR3)10X8]+ (X=Cl/Br) Clusters

The bonding character within metal nanoclusters represents an intriguing topic, shedding light on the inherent driving force for the packing preference in nanomaterials. Herein, density functional theory (DFT) calculations were conducted to investigate the correlation of the series of isomeric Au₁₃Ag₁₂(PR₃)₁₀X₈]⁺ (X=Cl/Br) clusters, which are mainly differentiated by the coordination mode of the equatorial halides (μ₂-, μ₃- and μ₄-) in the rod-like, bi-icosahedral framework. The theoretical simulation corroborates the variety in the configuration of the Au₁₃Ag₁₂ clusters and elucidates the fast isomerization kinetics among the different configurations. The easy tautomerization and the variety in chloride binding modes correspond to a fluxionality character of the equatorial halides and are verified by the potential energy curve analysis. The structural flexibility of the central Au₃Ag₁₀ block is the main driving force, while the relatively stronger Ag−X bonding interaction (compared to that of Au−X), and a sufficient number of halides are also requisite for the associating Ag−X tautomerizations.