Structural evolution and bonding properties of Au₂Si_n^−/0 (n = 1–7) clusters: Anion photoelectron spectroscopy and theoretical calculations

The photoelectron spectra of Au₂Si_n⁻ (n = 1–7) clusters were measured, and the structural evolution and bonding properties of Au₂Si_1–7⁻ anions and their corresponding neutral counterparts were investigated by theoretical calculations. The two Au atoms in Au₂Si_1–7^−/0 prefer to occupy low coordinate sites and form fewer Au–Si bonds. The aurophilic interaction is fairly weak in these clusters. The most stable structures of both Au₂Si_n⁻ anions and Au₂Si_n neutrals can be described as the two Au atoms interacting with the Si_n frameworks. The most stable isomers of Au₂Si_n⁻ anions are in spin doublet states, while those of the neutral clusters are in spin singlet states. The lowest-lying isomers of Au₂Si₁^−/0 have C_2v symmetric V-shaped structures. The global minimum of the Au₂Si₂⁻ anion has a D_2h symmetric planar rhombus structure, while that of the Au₂Si₂ neutral adopts a C_2v symmetric dibridged structure. In Au₂Si₃^−/0, the two Au atoms independently interact with the different Si–Si bonds of the Si₃ triangular structure. The global minima of Au₂Si_4–7^−/0 primarily adopt prismatic based geometries. Interestingly, Au₂Si₆^−/0 have significant 3D aromaticity and possess σ plus π double bonding characters, which play important roles in their structural stability.