title: Structural and theoretical basis for ligand exchange on thiolate monolayer protected gold nanoclusters.
abstract: Ligand exchange reactions are widely used for imparting new functionality on or integrating nanoparticles into devices. Thiolate-for-thiolate ligand exchange in monolayer protected gold nanoclusters has been used for over a decade; however, a firm structural basis of this reaction has been lacking. Herein, we present the first single-crystal X-ray structure of a partially exchanged Au(102)(p-MBA)(40)(p-BBT)(4) (p-MBA = para-mercaptobenzoic acid, p-BBT = para-bromobenzene thiol) with p-BBT as the incoming ligand. The crystal structure shows that 2 of the 22 symmetry-unique p-MBA ligand sites are partially exchanged to p-BBT under the initial fast kinetics in a 5 min timescale exchange reaction. Each of these ligand-binding sites is bonded to a different solvent-exposed Au atom, suggesting an associative mechanism for the initial ligand exchange. Density functional theory calculations modeling both thiol and thiolate incoming ligands postulate a mechanistic pathway for thiol-based ligand exchange. The discrete modification of a small set of ligand binding sites suggests Au(102)(p-MBA)(44) as a powerful platform for surface chemical engineering.
authors: Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
authors: Christine L
authors: CL
authors: Heinecke
authors: Thomas W
authors: TW
authors: Ni
authors: Sami
authors: S
authors: Malola
authors: Ville
authors: V
authors: Mäkinen
authors: O Andrea
authors: OA
authors: Wong
authors: Hannu
authors: H
authors: Häkkinen
authors: Christopher J
authors: CJ
authors: Ackerson
mesh_terms: D018360:Crystallography, X-Ray; D006046:Gold / Q000737:chemistry*; D008024:Ligands; D053768:Metal Nanoparticles / Q000737:chemistry*; D008958:Models, Molecular; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D008024:Ligands; D012997:Solvents; D006046:Gold