Department of Chemistry, Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, Xiangtan University, Hunan Province, China.
Nanoscale. 2012 Jul 21;4(14):4054-72. doi: 10.1039/c2nr30685a. Epub 2012 May 28.
Unlike bulk materials, the physicochemical properties of nano-sized metal clusters can be strongly dependent on their atomic structure and size. Over the past two decades, major progress has been made in both the synthesis and characterization of a special class of ligated metal nanoclusters, namely, the thiolate-protected gold clusters with size less than 2 nm. Nevertheless, the determination of the precise atomic structure of thiolate-protected gold clusters is still a grand challenge to both experimentalists and theorists. The lack of atomic structures for many thiolate-protected gold clusters has hampered our in-depth understanding of their physicochemical properties and size-dependent structural evolution. Recent breakthroughs in the determination of the atomic structure of two clusters, Au(25)(SCH(2)CH(2)Ph)(18) (q = -1, 0) and Au(102)(p-MBA)(44), from X-ray crystallography have uncovered many new characteristics regarding the gold-sulfur bonding as well as the atomic packing structure in gold thiolate nanoclusters. Knowledge obtained from the atomic structures of both thiolate-protected gold clusters allows researchers to examine a more general "inherent structure rule" underlying this special class of ligated gold nanoclusters. That is, a highly stable thiolate-protected gold cluster can be viewed as a combination of a highly symmetric Au core and several protecting gold-thiolate "staple motifs", as illustrated by a general structural formula AuAu(SR)(2)Au(2)(SR)(3)Au(3)(SR)(4)Au(4)(SR)(5) where a, a', b, c, d and e are integers that satisfy certain constraints. In this review article, we highlight recent progress in the theoretical exploration and prediction of the atomic structures of various thiolate-protected gold clusters based on the "divide-and-protect" concept in general and the "inherent structure rule" in particular. As two demonstration examples, we show that the theoretically predicted lowest-energy structures of Au(25)(SR)(8)(-) and Au(38)(SR)(24) (-R is the alkylthiolate group) have been fully confirmed by later experiments, lending credence to the "inherent structure rule".
与块状材料不同，纳米尺寸金属簇的物理化学性质可能强烈依赖于其原子结构和尺寸。在过去的二十年中，在合成和表征一类特殊的配体金属纳米簇方面取得了重大进展，即尺寸小于 2nm 的硫醇保护金纳米簇。然而，确定硫醇保护金纳米簇的精确原子结构仍然是实验家和理论家面临的一个巨大挑战。许多硫醇保护金纳米簇的原子结构尚未确定，这阻碍了我们对其物理化学性质和尺寸相关结构演化的深入理解。最近，通过 X 射线晶体学确定了两个金纳米簇的原子结构，即Au(25)(SCH(2)CH(2)Ph)(18)（q=-1,0）和 Au(102)(p-MBA)(44)，取得了突破性进展，揭示了金-硫键以及金硫醇纳米簇中的原子堆积结构的许多新特性。从硫醇保护金纳米簇的原子结构中获得的知识使研究人员能够检验这一特殊配体金纳米簇类的更一般的“固有结构规则”。也就是说，一个高度稳定的硫醇保护金纳米簇可以被看作是一个高度对称的 Au 核和几个保护金-硫醇“钉扎基序”的组合，如图所示一个一般的结构公式AuAu(SR)(2)Au(2)(SR)(3)Au(3)(SR)(4)Au(4)(SR)(5) 其中 a、a'、b、c、d 和 e 是满足某些约束的整数。在这篇综述文章中，我们强调了基于“分而治之”的概念，特别是基于“固有结构规则”，对各种硫醇保护金纳米簇的原子结构进行理论探索和预测的最新进展。作为两个示范例子，我们表明，理论预测的 Au(25)(SR)(8)(-)和 Au(38)(SR)(24)(-R 是烷基硫醇基团)的最低能量结构已被后来的实验完全证实，这证明了“固有结构规则”的合理性。
