Structural evolution and bonding properties of AuSi (n = 1-7) clusters: Anion photoelectron spectroscopy and theoretical calculations.

The photoelectron spectra of AuSi (n = 1-7) clusters were measured, and the structural evolution and bonding properties of AuSi anions and their corresponding neutral counterparts were investigated by theoretical calculations. The two Au atoms in AuSi 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 AuSi anions and AuSi neutrals can be described as the two Au atoms interacting with the Si frameworks. The most stable isomers of AuSi anions are in spin doublet states, while those of the neutral clusters are in spin singlet states. The lowest-lying isomers of AuSi have C symmetric V-shaped structures. The global minimum of the AuSi anion has a D symmetric planar rhombus structure, while that of the AuSi neutral adopts a C symmetric dibridged structure. In AuSi, the two Au atoms independently interact with the different Si-Si bonds of the Si triangular structure. The global minima of AuSi primarily adopt prismatic based geometries. Interestingly, AuSi have significant 3D aromaticity and possess σ plus π double bonding characters, which play important roles in their structural stability.