Deciphering the Ligand Exchange Process on Thiolate Monolayer Protected Au38(SR)24 Nanoclusters

Ligand exchange reactions are used widely to modify and tune the properties of thiolate monolayer protected nanoclusters. We employed density functional theory calculations to investigate the ligand exchange process on the Au-38(SH)(24) nanocluster. The Au-38 duster consists of eight possible unique sites for ligand exchange, including six sites from the dimeric staple motifs and two sites from monomeric units. The most favorable site for ligand exchange is found to be between a core gold atom and the -SH moiety on the monomeric unit. Ligand substitution between a core gold atom and a terminal -SH group or between a terminal -SH group and a staple gold atom at both sides of the dimer units is a more favorable site for the ligand exchange process than substitution of the central -SH moiety. However, substitution of the central -SH moiety on Au38 is more favorable than for the corresponding position on Au-25.