MALDI mass analysis of 11 kDa gold clusters protected by octadecanethiolate ligands

Risako Tsunoyama; Hironori Tsunoyama; Panvika Pannopard; Jumras Limtrakul; Tatsuya Tsukuda

doi:10.1021/jp101741a

MALDI mass analysis of 11 kDa gold clusters protected by octadecanethiolate ligands

Risako Tsunoyama, Hironori Tsunoyama, Panvika Pannopard, Jumras Limtrakul, Tatsuya Tsukuda

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

68 Citations (Scopus)

Abstract

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 _nH_2n+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.

Original language	English
Pages (from-to)	16004-16009
Number of pages	6
Journal	Journal of Physical Chemistry C
Volume	114
Issue number	38
DOIs	https://doi.org/10.1021/jp101741a
Publication status	Published - 2010 Sept 30

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Energy(all)
Physical and Theoretical Chemistry
Surfaces, Coatings and Films

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title = "MALDI mass analysis of 11 kDa gold clusters protected by octadecanethiolate ligands",

abstract = "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.",

author = "Risako Tsunoyama and Hironori Tsunoyama and Panvika Pannopard and Jumras Limtrakul and Tatsuya Tsukuda",

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AU - Tsunoyama, Risako

AU - Tsunoyama, Hironori

AU - Pannopard, Panvika

AU - Limtrakul, Jumras

AU - Tsukuda, Tatsuya

PY - 2010/9/30

Y1 - 2010/9/30

N2 - 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.

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MALDI mass analysis of 11 kDa gold clusters protected by octadecanethiolate ligands

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