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 Au102(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 minute time scale 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 Au102(p-MBA)44 as a powerful platform for surface chemical engineering.

Site-specific targeting of enterovirus capsid by functionalized monodisperse gold nanoclusters

“…In addition, gold nanoclusters allow potentially detailed (i) spectroscopic measurements of nanoclusters moving in relation to each other upon adding biochemical factors that lead to virus opening or (ii) manipulation of virus structure and function by using the fact that the clusters are strong absorbers of near-infrared radiation and generators of "local heat" upon deexcitation. Future work to refine the synthesis of maleimide linkers with tunable-length arms and impose fewer linkers per gold cluster by using ligandexchange kinetics (20,21), combined with control of concentration of clusters and time of incubation with viruses, may yield improved control of targeting desired cysteine groups at the surface of enteroviruses, e.g., close to positions that are currently thought of as critical for virus uncoating based on in vitro studies (22)(23)(24).…”

Ligand-Exchange-Induced Growth of an Atomically Precise Cu29 Nanocluster from a Smaller Cluster

“…[1][2] An emerging method for controlling the size and structure of nanoclusters involves ligand exchange to induce a transformation from one stable cluster to another. 1,[3][4][5][6] Although such ligand exchange reactions are commonly used to introduce new functional groups onto the surface of clusters while preserving the original core size, they can also lead to changes in the shape and/or size of the metal core. [3][4][5]7 24 ].…”

“…1,[3][4][5][6] Although such ligand exchange reactions are commonly used to introduce new functional groups onto the surface of clusters while preserving the original core size, they can also lead to changes in the shape and/or size of the metal core. [3][4][5]7 24 ]. 8 Similarly, thiolate ligand exchange mediates the conversion of a Ag 44 cluster into a smaller Ag 25 cluster.…”

The fate of Au25(SR)18 clusters upon ligand exchange with binaphthyl-dithiol: interstaple binding vs. decomposition

“…1- 13 The reactions allow convenient access to functionalized (e.g. chirally) monolayer-protected gold clusters.…”