We previously reported the isolation of octadecanethiolate-protected Au (Au:SC18H37) clusters having a core mass of ∼11 kDa from the crude Au:SC18H37 samples obtained in the reaction between octadecanethiol (C18H37SH) and poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized Au clusters. This stable Au:SC 18H37 compound was assigned to be Au55(SC nH2n+1)32 by destructive mass spectrometry and thermogravimetry (TG) performed in the framework of the classical structure model, in which the thiolates are bound to the surface of a magic Au 55 core. In the present study, the molecular formula of the Au:SC18H37 (11 kDa) cluster was reassessed by non-destructive matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), and it was confirmed that the Au:SC18H37 (11 kDa) cluster is a mixture of Au54(SC18H37) 30 and Au55(SC18H37)31. On the basis of our present understanding of the structures of other stable Au:SR clusters, we proposed that Au54(SC18H 37)30 and Au55(SC18H 37)31 have a structural motif comprising a Au37 cluster core that is completely protected by -SR-[Au(I)-SR-]x oligomers (x = 1 and 2). The nonformation of the Au:SR (11 kDa) cluster during the conventional chemical reduction of Au(I)-SR oligomers is ascribed to the kinetics of Au:SR formation.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films