Investigation on the Mechanism of the Synthesis of Gold(I) Thiolate Complexes by NMR

In this article, we characterized the polymeric gold(I) thiolates that precipitated from the intermediate solutions during the synthesis process of gold nanoparticles (GNPs) by the Brust–Schiffrin two-phase method and investigated the formation mechanism of the polymeric gold(I) thiolates. The solution 1 H NMR confirmed the complete reduction from Au(III) to Au(I) with the addition of the first two equivalents of thiols, while only the third and fourth equivalents of thiols were found to participate in forming gold(I) thiolates. Gold(I) thiolates, [Au(I)SR] n, precipitated from these solutions were further characterized by 1 H solid-state NMR spectroscopy under fast magic angle spinning (MAS), Raman spectroscopy, and thermogravimetric analysis. Further quantitative studies revealed that the composition of [Au(I)SR] n could be controlled by changing the order of addition of the third and fourth equivalents of thiols. This work has great significance to better understand the mechanism of gold nanoparticle formation and thus to tailor the properties of the final products.