Racemization of a chiral nanoparticle evidences the flexibility of the gold-thiolate interface

J Am Chem Soc. 2012 Aug 8;134(31):13114-20. doi: 10.1021/ja3053865. Epub 2012 Jul 26.

Abstract

Thiolate-protected gold nanoparticles and clusters combine size-dependent physical properties with the ability to introduce (bio)chemical functionality within their ligand shell. The engineering of the latter with molecular precision is an important prerequisite for future applications. A key question in this respect concerns the flexibility of the gold-sulfur interface. Here we report the first study on racemization of an intrinsically chiral gold nanocluster, Au38(SCH2CH2Ph)24, which goes along with a drastic rearrangement of its surface involving place exchange of several thiolates. This racemization takes place at modest temperatures (40-80 °C) without significant decomposition. The experimentally determined activation energy for the inversion reaction is ca. 28 kcal/mol, which is surprisingly low considering the large rearrangement. The activation parameters furthermore indicate that the process occurs without complete Au-S bond breaking.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, High Pressure Liquid
  • Circular Dichroism
  • Gold / chemistry*
  • Isomerism
  • Metal Nanoparticles / chemistry*
  • Spectrophotometry, Ultraviolet
  • Sulfhydryl Compounds / chemical synthesis
  • Sulfhydryl Compounds / chemistry*

Substances

  • Sulfhydryl Compounds
  • Gold