1 research outputs found
Structurally Similar Triphenylphosphine-Stabilized Undecagolds, Au<sub>11</sub>(PPh<sub>3</sub>)<sub>7</sub>Cl<sub>3</sub> and [Au<sub>11</sub>(PPh<sub>3</sub>)<sub>8</sub>Cl<sub>2</sub>]Cl, Exhibit Distinct Ligand Exchange Pathways with Glutathione
Ligand
exchange is frequently used to introduce new functional
groups on the surface of inorganic nanoparticles or clusters while
preserving the core size. For one of the smallest clusters, triphenylphosphine
(TPP)-stabilized undecagold, there are conflicting reports in the
literature regarding whether core size is retained or significant
growth occurs during exchange with thiol ligands. During an investigation
of these differences in reactivity, two distinct forms of undecagold
were isolated. The X-ray structures of the two forms, Au<sub>11</sub>(PPh<sub>3</sub>)<sub>7</sub>Cl<sub>3</sub> and [Au<sub>11</sub>(PPh<sub>3</sub>)<sub>8</sub>Cl<sub>2</sub>]ÂCl, differ only in the number
of TPP ligands bound to the core. Syntheses were developed to produce
each of the two forms, and their spectroscopic features correlated
with the structures. Ligand exchange on [Au<sub>11</sub>(PPh<sub>3</sub>)<sub>8</sub>Cl<sub>2</sub>]Cl yields only small clusters, whereas
exchange on Au<sub>11</sub>(PPh<sub>3</sub>)<sub>7</sub>Cl<sub>3</sub> (or mixtures of the two forms) yields the larger Au<sub>25</sub> cluster. The distinctive features in the optical spectra of the
two forms made it possible to evaluate which of the cluster forms
were used in the previously published papers and clarify the origin
of the differences in reactivity that had been reported. The results
confirm that reactions of clusters and nanoparticles may be influenced
by small variations in the arrangement of ligands and suggest that
the role of the ligand shell in stabilizing intermediates during ligand
exchange may be essential to preventing particle growth or coalescence