Electrospray mass spectrometry study of tiopronin monolayer-protected gold nanoclusters

J Am Chem Soc. 2007 Feb 7;129(5):1095-104. doi: 10.1021/ja0639057.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Chromatography, Gel / methods
  • Gold / chemistry*
  • Ligands
  • Nanostructures / chemistry*
  • Nanotechnology*
  • Organometallic Compounds / chemistry
  • Spectrometry, Mass, Electrospray Ionization / methods
  • Sulfhydryl Compounds / chemistry
  • Surface Properties
  • Tiopronin / chemistry*

Substances

  • Ligands
  • Organometallic Compounds
  • Sulfhydryl Compounds
  • Gold
  • Tiopronin