Doping of metal nanoclusters is an effective strategy for tailoring their functionalities for specific applications. To gain fundamental insight into the doping mechanism, it is of critical importance to have access to a series of correlated bimetal nanoclusters with different doping levels and further reveal the successive transformations. Herein, we report asymmetric doping of Ag into an Au21 nanocluster to form a series of new Au/Ag bimetal nanoclusters and the effects of doping on the evolution of size, structure, and properties based upon X-ray crystallography and optical spectroscopy analyses. The asymmetric doping discovered in the series reveals two important rules. First, the heteroatom doping-induced kernel transformation mechanism is revealed, explaining the successive conversions from Au21(S-Adm)15 with an incomplete cuboctahedral kernel to Au20Ag1(S-Adm)15 with a complete cuboctahedral Au12Ag1 kernel and then to Au19Ag4(S-Adm)15 with an icosahedral Au10Ag3 kernel. The electron density accumulated on the central Au atom(s) is rationalized to force an expansion of radial metal-metal bond angles, which triggers the cuboctahedral-to-icosahedral kernel conversion. This mechanism is generalized by elucidating several other cases. Second, through comparison of a series of seven nanoclusters (all protected by adamantanethiolate), we find that the unit cell symmetry of their crystals is correlated with the symmetry of the cluster's kernel. Specifically, we observe a sequential change from triclinic to monoclinic to trigonal unit cell in the series with increasing kernel symmetry. The kernel structure-dependent optical properties are also discussed.

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一系列相关的 Au/Ag 纳米团簇揭示了不对称 Ag 掺杂的演化模式

金属纳米团簇的掺杂是一种针对特定应用定制其功能的有效策略。为了从根本上了解掺杂机制，获得一系列具有不同掺杂水平的相关双金属纳米团簇并进一步揭示连续转变至关重要。在此，我们报告了将 Ag 不对称掺杂到 Au21 纳米团簇中以形成一系列新的 Au/Ag 双金属纳米团簇，以及基于 X 射线晶体学和光谱分析的掺杂对尺寸、结构和性质演变的影响。该系列中发现的不对称掺杂揭示了两个重要规则。首先，揭示了杂原子掺杂引起的核转变机制，解释了从具有不完整立方八面体内核的 Au21(S-Adm)15 到具有完整立方八面体 Au12Ag1 内核的 Au20Ag1(S-Adm)15，然后到具有二十面体 Au10Ag3 内核的 Au19Ag4(S-Adm)15 的连续转换。中心 Au 原子上积累的电子密度被合理化以迫使径向金属-金属键角扩大，从而触发立方八面体到二十面体核的转换。通过阐明其他几种情况可以概括这种机制。其次，通过比较一系列七个纳米团簇（均受金刚烷硫醇保护），我们发现它们晶体的晶胞对称性与团簇内核的对称性相关。具体而言，我们观察到随着核对称性的增加，系列中从三斜晶胞到单斜晶胞再到三角晶胞的顺序变化。