Electrospray mass spectrometry study of tiopronin monolayer-protected gold nanoclusters.

Gies AP, Hercules DM, Gerdon AE, Cliffel DE
J Am Chem Soc. 2007 129 (5): 1095-104

PMID: 17263390 · DOI:10.1021/ja0639057

Electrospray ionization time-of-flight mass spectrometry (ESI-TOF MS) and gel permeation chromatography (GPC) were used to study the synthesis of a series of tiopronin monolayer-protected gold nanoclusters (MPCs) and to monitor their postsynthesis peptide ligand place-exchange reactions. All mass spectra identified the presence of cyclic gold(I)-thiolates with a strong preference for tetrameric species. During the synthesis of pre-monolayer-protected nanoclusters (pre-MPCs), esterified gold(I)-thiolate tetramers were initially observed in minor abundance (with respect to disulfide bridged tiopronin species) before dramatically increasing in abundance and precipitating from solution. After conversion of pre-MPCs to MPCs, ESI-TOF mass spectra demonstrated an overall predominance of tetrameric species with conversion from ester-terminated end groups to carboxyl-terminated end groups. Further modifications were performed through postsynthesis ligand place-exchange reactions to validate the existence of the tetramers. This work suggests that monolayer protection is accomplished by cyclized gold(I)-thiolate tetramers on the gold core surface, and/or that gold(I)-thiolates are a basic building block within the nanoparticles.

MeSH Terms (10)

Chromatography, Gel Gold Ligands Nanostructures Nanotechnology Organometallic Compounds Spectrometry, Mass, Electrospray Ionization Sulfhydryl Compounds Surface Properties Tiopronin

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