Predictive Gold Nanocluster Formation Controlled by Metal-Ligand Complexes

Published

January 9, 2012

Author(s)

John M. Pettibone, Jeffrey W. Hudgens

Abstract

The formation of ligand-protected transition metal nanoclusters in size-selective syntheses is driven by the inherent properties of the protecting ligands. We have previously reported the selective, monodisperse product formation of phosphine protected Au₈, chlorinated Au₉ and Au₁₀ clusters, but a general description of how the ligands produce size-selective products is necessary to develop a predictive model for cluster formation. The current study used phosphine-protected Au clusters as a model system to examine i) the metal ligand complex distributions in methanol:chloroform solutions as a function of Au:ligand ratio, ii) the role of oxidation on the complex distribution and iii) nanocluster formation after reduction with NaBH₄ as a function of complex distribution. The initial complexes formed in solution are shown to not only control ligand formation, but also have strong correlation to specific synthetic pathways for product formation. Specifically, 1,n-bis(diphenylphosphino)alkane ligands, where n = 1-6 representing methane through hexane carbon backbones, are examined and split into two distinct classes based on Au:Lⁿ complex formation. The classes form predominately either [AuLⁿ₂]+ (Class I, n = 1-3) or [Au₂Lⁿ₂]²⁺ (Class II, n = 4-6) and the subsequent nanocluster formations after reduction are directly related to the initial complex distributions. Classification of the phosphine ligand:Au complexes allows for the first predictable syntheses of ligated Au clusters by simply monitoring the initial complex distribution.

Citation

Small

Volume

8

Issue

5

Pub Type

Journals

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Keywords

ESI-MS, nanoparticle, monodisperse, monolayer-protected cluster, nucleation, reduction

Citation

Pettibone, J. and Hudgens, J. (2012), Predictive Gold Nanocluster Formation Controlled by Metal-Ligand Complexes, Small, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908225 (Accessed April 23, 2024)