AuSi and AuSi: Electronically Equivalent but Different Polarity Superatoms.

A series of AuSi cluster anions ( = 1-4) were generated most abundantly by laser ablation of a AuSi alloy target. Photoelectron spectroscopy and density functional theory (DFT) calculation of AuSi ( = 1-4) revealed that AuSi can be viewed as an electronically closed superatom and is composed of a Si unit whose three adjacent edges of a single facet are bridged by three Au atoms. Such phase-segregated structure is facilitated by aurophilic interaction between the three Au atoms and results in a large permanent dipole moment (4.