We report a joint experimental and theoretical study on the structures of a series of gold clusters doped with a group-14 atom: MAux- (M = Si, Ge, Sn; x = 5-8). Well-resolved photoelectron spectra were obtained and compared to calculations at several levels of theory to identify the low-lying structures of MAu5-8-. We found that the structure of SiAu5- is dominated by the tetrahedrally coordinated Si motif, which can be viewed as built from the tetrahedral SiAu4-by an extra Au atom bonded to a terminal gold atom. However, SiAu6 - and SiAu7- have quasi-planar structures, similar to those of GeAu6-/SnAu6- and GeAu7-/SnAu7-, respectively. SiAu8- again has a tetrahedrally coordinated Si structure, which displays a structural motif of a dangling Au-Si unit sitting on a gold cluster surface, resembling that of the larger Si-doped gold cluster SiAu 16-. For M = Ge, Sn, our results show that the major isomers of GeAu5-8- have structures similar to those of the corresponding SnAu5-8- clusters, and they can be viewed as grown from the previously suggested square-pyramidal GeAu 4- and SnAu4-, respectively. Population of minor isomers was observed for SnAu5-, GeAu6-, SnAu6-, and GeAu 8-. The 3D to quasi-2D to 3D structural evolution for SiAu5- to SiAu8- and the structural convergence for MAux- (M = Si, Ge, Sn) at x = 6, 7 manifest competitions between the tendency of forming molecule-like structures around the group-14 dopant (optimizing M-Au interactions) and the strong tendency of forming planar structures for small gold anion clusters (optimizing Au-Au interactions).
ASJC Scopus subject areas
- Colloid and Surface Chemistry