Au-40(SR)(24) Cluster as a Chiral Dimer of 8-Electron Superatoms: Structure and Optical Properties

作者：Malola Sami; Lehtovaara Lauri; Knoppe Stefan; Hu Kuo Juei; Palmer Richard E; Buergi Thomas; Hakkinen Hannu^*

来源：Journal of the American Chemical Society, 2012, 134(48): 19560-19563.

DOI：10.1021/ja309619n

We predict and analyze density-functional theory (DFT)-based structures for the recently isolated Au-40(SR)(24) cluster. Combining structural information extracted from ligand-exchange reactions, circular dichroism and transmission electron microscopy leads us to propose two families of low-energy structures that have a chiral Au-S framework on the surface. These families have a common geometrical motif where a nonchiral Au-26 bi-icosahedral cluster core is protected by 6 RS-Au-SR and 4 RS-Au-SR-Au-SR oligomeric units, analogously to the %26quot;Divide and Protect%26quot; motif of known clusters Au-25(SR)(18)(-/0), Au-38(SR)(24) and Au-102(SR)(44). The strongly prolate shape of the proposed Au26 core is supported by transmission electron microscopy. Density-of-state-analysis shows that the electronic structure of Au-40(SR)(24) can be interpreted in terms of a dimer of two 8-electron superatoms, where the 8 shell electrons are localized at the two icosahedral halves of the metal core. The calculated optical and chiroptical characteristics of the optimal chiral structure are in a fair agreement with the reported data for Au-40(SR)(24).

• 出版日期2012-12-5