Department of Physical Chemistry, University of Geneva , 30 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
J Am Chem Soc. 2012 Aug 8;134(31):13114-20. doi: 10.1021/ja3053865. Epub 2012 Jul 26.
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.
硫醇保护的金纳米粒子和团簇将尺寸相关的物理性质与在其配体壳中引入（生物）化学功能的能力结合在一起。通过分子精度对后者进行工程设计是未来应用的重要前提。在这方面的一个关键问题涉及到金-硫界面的灵活性。在这里，我们报告了首例关于手性金纳米团簇 Au38(SCH2CH2Ph)24 消旋的研究，该研究伴随着其表面的剧烈重排，涉及几个硫醇的位置交换。这种消旋反应在适中的温度（40-80°C）下发生，没有明显的分解。实验确定的反转反应的活化能约为 28 kcal/mol，考虑到较大的重排，这令人惊讶地低。活化参数还表明，该过程不会导致 Au-S 键完全断裂。
