Au₃Si₄^– and Au₄Si₄: Electronically Equivalent but Different Polarity Superatoms

Abstract

A series of Au x Si4 – cluster anions (x = 1–4) were generated most abundantly by laser ablation of a Au4Si alloy target. Photoelectron spectroscopy and density functional theory (DFT) calculation of Au x Si4 – (x = 1–4) revealed that Au3Si4 – can be viewed as an electronically closed superatom and is composed of a Si4 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 (4.43 D). DFT calculations on an electronically equivalent superatom Au4Si4 predicted a new structure in which the uncoordinated Si atom of Au3Si4 – is bonded by Au+. This Au4Si4 is much more stable than a cubic structure previously reported and has a large HOMO–LUMO gap (1.68 eV) and a small permanent dipole moment (0.41 D).

Virtual Issue on Experiment–Theory Synergies in the Study of Metal and Metal-Containing Clusters

“…This study elucidated the evolution from planar to low-symmetry (amorphous) to crystal structure fragments ( n = 12, 13) for surprisingly small species. Similarly, anion photoelectron (PE) spectra − of clusters can be assigned with supporting calculations and their associated spectral simulations. The calculations can then reveal features that may not be immediately obvious from the experimental spectra.…”

“…Multiple competitive isomers and fluxionality was elucidated in DFT calculations that accompanied the PE spectra of Al n Pt – . Koyasu et al leveraged DFT calculations in the interpretation of their anion PE spectra of Au 3 Si 4 – and Au 4 Si 4 – to demonstrate superatomicity, but different polarities, of Au 3 Si 4 – and Au 4 Si 4 0 …”