Probing the Structural Evolution of Gold–Aluminum Bimetallic Clusters (Au2Aln–, n = 3–11) Using Photoelectron Spectroscopy and Theoretical Calculations

We report a combined photoelectron spectroscopy and theoretical study of the structural evolution of aluminum cluster anions doped with two gold atoms, Au2Aln– (n = 3–11). Well-resolved photoelectron spectra have been obtained at several photon energies and are used to compare with theoretical calculations to elucidate the structures of the bimetallic clusters. Global minima of the Au2Aln– clusters were searched using the basin-hopping method combined with density functional theory calculations. Vertical detachment energies were computed for the low-lying isomers with the inclusion of spin–orbit effects and were used to generate simulated photoelectron spectra. Au2Al2– was previously found to exhibit a tetrahedral structure, whereas Au2Al3– is found currently to be planar. Beyond n = 3, the global minima of Au2Aln– are dominated by three-dimensional structures. A robust square-bipyramidal Al6 motif is observed for n = 6–9, leading to a highly stable tubular-like global minimum for Au2Al9–. Compact three-d...