Control of single-ligand chemistry on thiolated Au25 nanoclusters

Diverse methods have been developed to tailor the number of metal atoms in metal nanoclusters, but control of surface ligand number at a given cluster size is rare. Here we demonstrate that reversible addition and elimination of a single surface thiolate ligand (-SR) on gold nanoclusters can be realized, opening the door to precision ligand engineering on atomically precise nanoclusters. We find that oxidative etching of [Au25SR18](-) nanoclusters adds an excess thiolate ligand and generates a new species, [Au25SR19](0). The addition reaction can be reversed by CO reduction of [Au25SR19](0), leading back to [Au25SR18](-) and eliminating precisely one surface ligand. Intriguingly, we show that the ligand shell of Au-25 nanoclusters becomes more fragile and rigid after ligand addition. This reversible addition/elimination reaction of a single surface ligand on gold nanoclusters shows potential to precisely control the number of surface ligands and to explore new ligand space at each nuclearity. Diverse methods have been developed to tailor the number of metal atoms in metal nanoclusters, but controlling the number of surface ligands is rare. Here, the authors realize reversible addition and elimination of a single thiolate ligand on a gold nanocluster.