Zhu Manzhou, Aikens Christine M, Hollander Frederick J, Schatz George C, Jin Rongchao
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvannia 15213, USA.
J Am Chem Soc. 2008 May 7;130(18):5883-5. doi: 10.1021/ja801173r. Epub 2008 Apr 12.
The total structure determination of thiol-protected Au clusters has long been a major issue in cluster research. Herein, we report an unusual single crystal structure of a 25-gold-atom cluster (1.27 nm diameter, surface-to-surface distance) protected by eighteen phenylethanethiol ligands. The Au25 cluster features a centered icosahedral Au13 core capped by twelve gold atoms that are situated in six pairs around the three mutually perpendicular 2-fold axes of the icosahedron. The thiolate ligands bind to the Au25 core in an exclusive bridging mode. This highly symmetric structure is distinctly different from recent predictions of density functional theory, and it also violates the empirical golden rule "cluster of clusters", which would predict a biicosahedral structure via vertex sharing of two icosahedral M13 building blocks as previously established in various 25-atom metal clusters protected by phosphine ligands. These results point to the importance of the ligand-gold core interactions. The Au25(SR)18 clusters exhibit multiple molecular-like absorption bands, and we find the results are in good correspondence with time-dependent density functional theory calculations for the observed structure.
硫醇保护的金团簇的完整结构测定长期以来一直是团簇研究中的一个主要问题。在此，我们报道了一种由十八个苯乙硫醇配体保护的25个金原子团簇（直径1.27 nm，表面到表面距离）的不寻常单晶结构。Au25团簇的特征是一个中心二十面体Au13核，由十二个金原子封顶，这些金原子位于围绕二十面体三个相互垂直的2重轴的六对位置。硫醇盐配体以独特的桥连模式与Au25核结合。这种高度对称的结构与最近密度泛函理论的预测明显不同，并且还违反了经验法则“团簇的团簇”，该法则通过两个二十面体M13构建块的顶点共享预测双二十面体结构，正如之前在各种由膦配体保护的25原子金属团簇中所确立的那样。这些结果表明配体 - 金核相互作用的重要性。Au25(SR)18团簇表现出多个类似分子的吸收带，并且我们发现结果与针对观察到的结构的含时密度泛函理论计算结果非常吻合。
