One-pot synthesis of Au144(SCH2Ph)60 nanoclusters and their catalytic application

Abstract

Here, we report the one-pot synthesis of atomically precise gold nanoclusters – Au₁₄₄(SCH₂Ph)₆₀ with moderate efficiency (ca. 20% yield based on HAuCl₄). The Au₁₄₄(SCH₂Ph)₆₀ nanoclusters are obtained from the polydispersed Au_n(SG)_m nanoclusters in the presence of excess H–SCH₂Ph ligands via a combination of “ligand-exchange” and “size-focusing” processes. The as-obtained Au₁₄₄(SCH₂Ph)₆₀ nanoclusters are well determined by UV-vis spectroscopy and electrospray ionization (ESI) mass spectrometry, and in conjunction with matrix-assisted laser desorption ionization (MALDI) mass spectrometry and thermal gravimetric analysis (TGA). The purity of the Au₁₄₄(SCH₂Ph)₆₀ nanoclusters is further characterized by size exclusion chromatography (SEC) and elemental analysis. The powder X-ray diffraction (PXRD) analysis implies that the Au₁₄₄(SCH₂Ph)₆₀ nanoclusters do not adopt the face-centered cubic (fcc) structure, as the diffraction angle (2θ = 50.5°) is only observed in the Au₁₄₄(SCH₂Ph)₆₀ nanoclusters. Further, the Au₁₄₄(SCH₂Ph)₆₀/TiO₂ catalyst exhibits excellent catalytic performance (92% conversion of methyl phenyl sulfide with 99% selectivity for sulfoxide) in the selective sulfoxidation; size-dependence of the gold nanocluster catalyst is observed in the catalytic reactions: Au₁₄₄(SCH₂Ph)₆₀ > Au₉₉(SPh)₄₂ > Au₃₈(SCH₂CH₂Ph)₂₄ > Au₂₅(SCH₂CH₂Ph)₁₈.