摘要/Abstract

原子精确的纳米硫银团簇由于其迷人的结构特征和潜在的应用价值而受到研究者的广泛关注.本工作通过溶液自组装的方法合成了两个新型核壳结构的硫银团簇[Ag₅₆S₁₂（^tBuS）₂₀（CF₃CO₂）₁₂]·6CH₃CN·8H₂O（Ag₅₆）和[Ag₅₈S₁₂-（^tBuS）₂₀（CF₃CO₂）₁₄（CH₃CN）₆]·6CH₃CN（Ag₅₈）.单晶XRD结构表征表明两个硫银团簇的内部均包裹着Ag₁₄单元：Ag₅₆中Ag₁₄内核单元为常见菱形十二面体结构，而Ag₅₈中Ag₁₄内核单元为罕见的纺锤形结构.Ag₁₄内核单元的异构引起了两个硫银团簇外壳结构和形貌的变化，相比于Ag₅₆中12个Ag₆环形结构单元相互连接形成的球状外壳，Ag₅₈的外层银原子按照“Ag₄-Ag₈-Ag₁₀-Ag₁₀-Ag₈-Ag₄”层状分布的方式形成了纺锤形外壳.紫外-可见吸收光谱和荧光光谱研究表明，硫银团簇Ag₅₆和Ag₅₈结构的差异对其能级以及荧光性质都会产生影响.本工作中两个新型硫银团簇的成功分离丰富了硫银团簇的研究体系和结构类型，并为进一步探究硫银团簇的形成过程和性质提供了新的思路.
关键词: 硫银团簇, Ag₁₄, 结构异构, 自组装
The atomically precise silver(I)-thiolate clusters in nanoscale have attracted extensive attention for years due to their attractive aesthetic structures and potential applications. Herein, two novel core-shell structured silver(I)-thiolate clusters of [Ag₅₆S₁₂(^tBuS)₂₀(CF₃CO₂)₁₂]·6CH₃CN·8H₂O (abbreviated as Ag₅₆) and [Ag₅₈S₁₂(^tBuS)₂₀(CF₃CO₂)₁₄(CH₃CN)₆]·6CH₃CN (Ag₅₈) are prepared by employing the self-assembly method in solution. Especially, with the introduction of dimethylformamide (DMF) and bis(diphenylphosphino)methane (DPPM), the ^tBuSAg precursor reacted with CF₃CO₂Ag to produce a novel cluster Ag₅₈ instead of Ag₅₆ that has a similar structure with previous reports. X-ray structural analysis indicates that both clusters have Ag₁₄ core units. But different from the common dodecahedron structure in Ag₅₆, the spindle-shaped Ag₁₄ structure in Ag₅₈ is discovered for the first time and then induces the shell structure of Ag₅₈ to form a rare spindle shape, in which silver atoms are layered in a form of “Ag₄-Ag₈-Ag₁₀-Ag₁₀-Ag₈-Ag₄”. Notably, the spindle-shaped Ag₁₄ is formed by rhombic dodecahedron being symmetrically pulled outward. Thus, there are obvious similarities and differences between the two Ag₁₄ core structures. Compared with the previously reported the face-centered cubic Ag₁₄ prepared by solvothermal methods, the rhombic dodecahedron and the rhombic dodecahedron-like (spindle) Ag₁₄ were obtained at room temperature, which indicates that the formation of the clusters is a thermodynamic control. However, the change of solvent and auxiliary ligands also caused the Ag₁₄ rhombohedral dodecahedron to deform and transform into a spindle-shaped structure, proving that the formation of the clusters is also a process controlled by kinetics. These prove that the synthesis of clusters is a process dominated by both of kinetics and thermodynamics. The UV-Vis absorption and fluorescence spectra show that the structure discrepancies of the two clusters deriving from the isomerization of Ag₁₄ units significantly affect the energy levels and fluorescence properties of the clusters. This study enriches the thiolate-silver cluster family and provides new samples and insights for understanding the formation mechanism and properties of such core-shell architectures.
Key words: silver(I)-thiolate clusters, Ag₁₄, isomerization, self-assembly


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