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Atomically precise Au144(SR)60 nanoclusters (R = Et, Pr) are capped by 12 distinct ligand types of 5-fold equivalence and display gigantic diastereotopic effects†
Chemical Science ( IF 7.6 ) Pub Date : 2018-11-07 00:00:00 , DOI: 10.1039/c8sc04092c
Tiziano Dainese 1 , Mikhail Agrachev 1 , Sabrina Antonello 1 , Denis Badocco 1 , David M Black 2 , Alessandro Fortunelli 3 , José A Gascón 4 , Mauro Stener 5 , Alfonso Venzo 6 , Robert L Whetten 2 , Flavio Maran 1, 4
Affiliation  

For two decades, Au144(SR)60 has been one of the most studied and used thiolate (SR) protected gold nanoclusters. In many ways, however, it proved to be a challenging and elusive case, also because of the difficulties in solving its structure by single-crystal X-ray crystallography. We used very short thiols and could prepare Au144(SC2H5)60 and Au144(SC3H7)60 in a very pure form, which was confirmed by UV-vis absorption spectroscopy and very regular electrochemistry patterns. Inductively coupled plasma and electrospray ionization mass spectrometries gave definite proof of the Au144(SR)60 stoichiometry. High-resolution 1D and 2D NMR spectroscopy in the solution phase provided the result of assessing the presence of 12 ligand types in exactly the same amount (5-fold equivalence). Equally important, we found that the two protons belonging to each methylene group along the thiolate chain are diastereotopic. For the α-CH2 protons, the diastereotopic effect can be indeed gigantic, as it reaches chemical-shift differences of 2.9 ppm. DFT calculations provided insights into the relationship between structure and NMR results. In particular, the 12 ligand types and corresponding diastereotopic effects may be explained by considering the presence of C–H⋯S hydrogen bonds. These results thus provide fundamental insights into the structure of the thiolate layer capping this long-studied gold nanocluster.

中文翻译:


原子精确的 Au144(SR)60 纳米团簇 (R = Et, Pr) 被 12 种不同的 5 倍等价配体类型所覆盖,并显示出巨大的非对映效应†



二十年来,Au 144 (SR) 60一直是研究和使用最多的硫醇盐 (SR) 保护的金纳米团簇之一。然而,在许多方面,它被证明是一个具有挑战性和难以捉摸的案例,也是因为通过单晶 X 射线晶体学解析其结构存在困难。我们使用非常短的硫醇,可以制备非常纯的Au 144 (SC 2 H 5 ) 60和Au 144 (SC 3 H 7 ) 60 ,这通过紫外可见吸收光谱和非常规则的电化学模式得到证实。电感耦合等离子体和电喷雾电离质谱明确证明了 Au 144 (SR) 60 的化学计量。溶液相中的高分辨率 1D 和 2D NMR 光谱提供了评估 12 种配体类型是否存在的结果,其数量完全相同(5 倍当量)。同样重要的是,我们发现沿着硫醇盐链属于每个亚甲基的两个质子是非对映异构体。对于 α-CH 2质子,非对映效应确实是巨大的,因为它的化学位移差异达到 2.9 ppm。 DFT 计算提供了对结构和 NMR 结果之间关系的深入了解。特别是,12 种配体类型和相应的非对映效应可以通过考虑 C–H⋯S 氢键的存在来解释。 因此,这些结果为覆盖这个长期研究的金纳米簇的硫醇盐层的结构提供了基本的见解。
更新日期:2018-11-07
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