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

Here, we report the one-pot synthesis of atomically precise gold nanoclusters - Au-144(SCH2Ph)(60) with moderate efficiency (ca. 20% yield based on HAuCl4). The Au-144(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 Au-144(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 Au-144(SCH2Ph)(60) nanoclusters is further characterized by size exclusion chromatography (SEC) and elemental analysis. The powder X-ray diffraction (PXRD) analysis implies that the Au-144(SCH2Ph)(60) nanoclusters do not adopt the face-centered cubic (fcc) structure, as the diffraction angle (2 theta = 50.5 degrees) is only observed in the Au-144(SCH2Ph)(60) nanoclusters. Further, the Au-144(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: Au-144(SCH2Ph)(60) > Au-99(SPh)(42) > Au-38(SCH2CH2Ph)(24) > Au-25(SCH2CH2Ph)(18).