Pei Yong, Wang Pu, Ma Zhongyun, Xiong Lin
College of Chemistry, Key Laboratory for Green Organic Synthesis and Application of Hunan Province, Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education , Xiangtan University , Xiangtan , Hunan 411105 , China.
Acc Chem Res. 2019 Jan 15;52(1):23-33. doi: 10.1021/acs.accounts.8b00385. Epub 2018 Dec 14.
Understanding the structure and structure-property relationship of atomic and ligated clusters is one of the central research tasks in the field of cluster research. In chemistry, empirical rules such as the polyhedral skeleton electron pair theory (PSEPT) approach had been outlined to account for skeleton structures of many main-group atomic and ligand-protected transition metal clusters. Nonetheless, because of the diversity of cluster structures and compositions, no uniform structural and electronic rule is available for various cluster compounds. Exploring new cluster structures and their evolution is a hot topic in the field of cluster research for both experiment and theory. In this Account, we introduce our recent progress in the theoretical exploration of structures and evolution patterns of a class of atomically precise thiolate-protected gold nanoclusters using density functional theory computations. Unlike the conventional ligand-protected transition metal compounds, the thiolate-protected gold clusters demonstrate novel metal core/ligand shell interfacial structures in which the Au (SR) clusters can be divided into an ordered Au(0) core and a group of oligomeric SR[Au(SR)] ( x = 0, 1, 2, 3, ...) protection motifs. Guided by this "inherent structure rule", we have devised theoretical methods to rapidly explore cluster structures that do not necessarily require laborious global potential energy surface searches. The structural predictions of Au(SR), Au(SR), and Au(SR) nanoclusters were completely or partially verified by the later X-ray crystallography studies. On the basis of the analysis of cluster structures determined by X-ray crystallography and theoretical prediction, a structural evolution diagram for the face-centered-cubic (fcc)-type Au (SR) clusters with m up to 92 has been preliminarily established. The structural evolution diagram indicates some basic structural and electronic evolution patterns of thiolate-protected gold nanoclusters. The fcc Au (SR) clusters show a genetic structural evolution pattern in which each step of cluster size increase results in the formation of another Au tetrahedron or Au triangle unit in the Au core, and every increase of a structural unit in the Au core leads to an increase of two electrons in the whole cluster. The unique one- or two-dimensional cluster size evolution, the isomerism of the Au-S framework, and the formation of a double-helical and cyclic tetrahedron network in the fcc Au (SR) clusters all can be addressed from this evolution pattern. The summarized cluster structural evolution diagrams enable us to further explore more stable cluster structures and understand their structure-electronic structure-property relationships.
理解原子簇和配位簇的结构以及结构 - 性质关系是簇研究领域的核心研究任务之一。在化学领域，已经概述了诸如多面体骨架电子对理论（PSEPT）方法等经验规则，以解释许多主族原子簇和配体保护的过渡金属簇的骨架结构。然而，由于簇结构和组成的多样性，对于各种簇化合物不存在统一的结构和电子规则。探索新的簇结构及其演化是簇研究领域中实验和理论方面的热门话题。在本综述中，我们介绍了我们最近使用密度泛函理论计算对一类原子精确的硫醇盐保护的金纳米簇的结构和演化模式进行理论探索的进展。与传统的配体保护的过渡金属化合物不同，硫醇盐保护的金簇展示了新颖的金属核/配体壳界面结构，其中Au(SR)簇可分为有序的Au(0)核和一组低聚SR[Au(SR)]（x = 0, 1, 2, 3, ...）保护基序。在这个“固有结构规则”的指导下，我们设计了理论方法来快速探索簇结构，不一定需要费力地进行全局势能面搜索。Au(SR)、Au(SR)和Au(SR)纳米簇的结构预测后来通过X射线晶体学研究得到了完全或部分验证。在对由X射线晶体学确定的簇结构和理论预测进行分析的基础上，初步建立了面心立方（fcc）型Au(SR)簇（m高达92）的结构演化图。该结构演化图表明了硫醇盐保护的金纳米簇的一些基本结构和电子演化模式。fcc Au(SR)簇呈现出一种遗传结构演化模式，其中簇尺寸增加的每一步都会导致在Au核中形成另一个Au四面体或Au三角形单元，并且Au核中每个结构单元的增加会导致整个簇中电子数增加两个。fcc Au(SR)簇中独特的一维或二维簇尺寸演化、Au - S框架的异构现象以及双螺旋和环状四面体网络的形成都可以从这种演化模式中得到解释。总结的簇结构演化图使我们能够进一步探索更稳定的簇结构，并理解它们的结构 - 电子结构 - 性质关系。
