Missing All-Thiolate Icosahedral Au₁₃ Superatom Nanocluster: A Catalytically Active Supramolecular Assembly.

Abstract

Magic atom-number Au₁₃ icosahedral nanoclusters containing a central Au atom surrounded by 12 Au atoms have been known for almost half a century with various ligands. However, such a cluster with all 12 peripheral Au atoms ligated by 12 thiolates, which is an obvious target, is not known. Herein, we report this missing icosahedral Au₁₃ superatom nanocluster as a supramolecular assembly prepared by a two-phase exchange method, protected by a double layer of 12 thiolate ligands and electrostatically stabilized by eight <i>t</i>-butyl ammonium groups. A recyclable heterogeneous catalyst, prepared by wet impregnation of the Au₁₃ cluster onto multiwall carbon nanotubes (CNTs), is active for the oxidative coupling of aniline, as demonstrated by mass spectrometry, which shows the exchange of a cluster amine with aniline. This catalyst is superior to catalysts obtained upon thermal ligand removal. A series of reaction intermediates were successfully captured, including the superoxide radical anion, as confirmed by electron paramagnetic resonance (EPR) analysis and density functional theory (DFT) calculations disentangling the catalytic reaction mechanism.