Structural and theoretical basis for ligand exchange on thiolate monolayer protected gold nanoclusters.
Structural and theoretical basis for ligand exchange on thiolate monolayer protected gold nanoclusters.
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DOI：
10.1021/ja3032339
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发表时间：
2012-08-15
影响因子：
15
通讯作者：
Ackerson CJ
中科院分区：
文献类型：
--
作者：
Heinecke CL;Ni TW;Malola S;Mäkinen V;Wong OA;Häkkinen H;Ackerson CJ
配体交换反应广泛用于赋予纳米颗粒新的功能或将纳米颗粒整合到装置中。在单层保护的金纳米团簇中硫醇盐-对-硫醇盐配体交换已经使用了十多年;然而，这种反应缺乏坚实的结构基础。在此，我们提出了第一个单晶X-射线结构的部分交换的Au 102（p-MBA）40（p-BBT）4（p-MBA =对巯基苯甲酸，p-BBT =对溴苯硫酚）与p-BBT作为传入的配体。晶体结构表明，在5分钟的时间尺度交换反应中，22个独特的p-MBA配体位点中的2个在初始快速动力学下部分交换为p-BBT。这些配体结合位点中的每一个结合到不同的溶剂暴露的Au原子，这表明初始配体交换的缔合机制。模拟硫醇和硫醇盐引入配体的密度泛函理论计算假定基于硫醇的配体交换的机械途径。一小组配体结合位点的离散修饰表明Au 102（p-MBA）44是表面化学工程的有力平台。
Ligand exchange reactions are widely used for imparting new functionality on or integrating nanoparticles into devices. Thiolate - for - thiolate ligand exchange in monolayer protected gold nanoclusters has been used for over a decade; however, a firm structural basis of this reaction has been lacking. Herein, we present the first single-crystal X-ray structure of a partially exchanged Au102(p-MBA)40(p-BBT)4 (p-MBA = para-mercaptobenzoic acid, p-BBT = para-bromobenzene thiol) with p-BBT as the incoming ligand. The crystal structure shows that 2 of the 22 symmetry-unique p-MBA ligand sites are partially exchanged to p-BBT under the initial fast kinetics in a 5 minute time scale exchange reaction. Each of these ligand-binding sites is bonded to a different solvent exposed Au atom, suggesting an associative mechanism for the initial ligand exchange. Density functional theory calculations modeling both thiol and thiolate incoming ligands postulate a mechanistic pathway for thiol based ligand exchange. The discrete modification of a small set of ligand binding sites suggests Au102(p-MBA)44 as a powerful platform for surface chemical engineering.