Interconversion between Superatomic 6-Electron and 8-Electron Configurations of M@Au24(SR)18 Clusters (M = Pd, Pt)
Interconversion between Superatomic 6-Electron and 8-Electron Configurations of M@Au24(SR)18 Clusters (M = Pd, Pt)
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DOI：
10.1021/jacs.5b06946
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发表时间：
2015-08-26
影响因子：
15
通讯作者：
Lee, Dongil
中科院分区：
文献类型：
--
作者：
Kwak, Kyuju;Tang, Qing;Lee, Dongil
硫醇盐保护的Au-25簇合物[Au-25（SR）（18）]（-）的异常稳定性源于超原子电子壳层的闭合，导致类似稀有气体的8电子构型（1 S（2）1 P（6））。在这里，我们提出用Pd或Pt取代中心Au原子，得到稳定的[MAu 24（SR）（18）]（0）团簇（M = Pd，Pt），具有超原子六电子构型（1 S（2）1 P（4））。对[PdAu 24（SR）（18）]（0）和[PtAu 24（SR）（18）]（0）的伏安研究表明，这些团簇的最高占据分子轨道-最低未占分子轨道（HOMO-LUMO）能隙分别为0.32和0.29 eV，表明它们的电子结构在杂质金属掺杂后发生了剧烈的改变。密度泛函研究证实，这些团簇的HOMO-LUMO能隙确实比[Au-25（SR）（18）]（-）（1.35 eV）小，分别为0.33和0.32 eV。对6电子[MAu 24（SR）（18）]团簇的优化几何结构的分析表明，MAu 12的核心略微扁平，产生扁椭圆体。因此，观察到的HOMO-LUMO能隙的急剧减小是6电子[MAu 24（SR）（18）]（0）团簇的Jahn-Teller样畸变的结果，伴随着1 P轨道的分裂。这些团簇在电子充电时变成8电子[MAu 24（SR）（18）]（2-）团簇，证明了MAu 24（SR）（18）的6电子和8电子构型之间的可逆相互转化。
The exceptional stability of thiolate-protected Au-25 clusters, [Au-25(SR)(18)](-), arises from the closure of superatomic electron shells, leading to a noble-gas-like 8-electron configuration (1S(2)1P(6)). Here we present that replacing the core Au atom with Pd or Pt results in stable [MAu24(SR)(18)](0) clusters (M = Pd, Pt) having a superatomic 6-electron configuration (1S(2)1P(4)). Voltammetric studies of [PdAu24(SR)(18)](0) and [PtAu24(SR)(18)](0) reveal that the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of these clusters are 0.32 and 0.29 eV, respectively, indicating their electronic structures are drastically altered upon doping of the foreign metal. Density functional investigations confirm that the HOMO-LUMO gaps of these clusters are indeed smaller, respectively 0.33 and 0.32 eV, than that of [Au-25(SR)(18)](-) (1.35 eV). Analysis of the optimized geometries for the 6-electron [MAu24(SR)(18)] clusters shows that the MAu12 core is slightly flattened to yield an oblate ellipsoid. The drastically decreased HOMO-LUMO gaps observed are therefore the result of Jahn-Teller-like distortion of the 6-electron [MAu24(SR)(18)](0) clusters, accompanying splitting of the 1P orbitals. These clusters become 8-electron [MAu24(SR)(18)](2-) clusters upon electronic charging, demonstrating reversible interconversion between the 6-electron and 8-electron configurations of MAu24(SR)(18).