Molecular Electron-Transfer Properties of Au₃₈ Clusters

The electron transfer (ET) properties of Au38 clusters protected by a phenylethanethiolate monolayer, Au38(SR)24, were studied in N,N-dimethylformamide and dichloromethane. The kinetic parameters of the first oxidation steps (+1/0 and +2/+1) and the first reduction step (0/−1) were obtained by electrochemical methods. The anion electrogenerated from Au38(SR)24 was employed in homogeneous redox catalysis experiments, using diphenyl disulfide and benzyl bromide as the acceptors. Both the heterogeneous and the homogeneous analyses pointed to the fast ET behavior typical for the formation and reactivity of delocalized ionic species with small intrinsic barriers. The results show that Au38 clusters are in all respects efficient redox molecules

Effect of Peptide Ligand Dipole Moments on the Redox Potentials of Au₃₈ and Au₁₄₀ Nanoparticles^†

Phenylethanethiolate monolayer-protected Au38 and Au140 nanoclusters were modified by ligand place exchange with a series of thiolated peptides. The peptides were homooligomers based on the α-aminoisobutyiric acid unit. The effects of changing the peptide concentration and the peptide length in the capping monolayer were studied by differential pulse voltammetry. The results showed that the redox behavior of the nanoparticles can be affected very significantly by such modifications. For example, the first oxidation peak of Au38, a cluster displaying molecule-like behavior, could be shifted positively by as much as 0.7−0.8 V. Detectable redox shifts were noted even when one single oriented peptide was in the Au140 monolayer. These effects were attributed to the molecular dipole moments of the peptide ligands