title: Au40(SR)24 cluster as a chiral dimer of 8-electron superatoms: structure and optical properties.
abstract: 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 "Divide and Protect" 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 Au(26) 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).
authors.affiliation: Department of Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland.
authors.forename: Sami
authors.initials: S
authors.lastname: Malola
authors.forename: Lauri
authors.initials: L
authors.lastname: Lehtovaara
authors.forename: Stefan
authors.initials: S
authors.lastname: Knoppe
authors.forename: Kuo-Juei
authors.initials: KJ
authors.lastname: Hu
authors.forename: Richard E
authors.initials: RE
authors.lastname: Palmer
authors.forename: Thomas
authors.initials: T
authors.lastname: Bürgi
authors.forename: Hannu
authors.initials: H
authors.lastname: Häkkinen
mesh_terms: D002942:Circular Dichroism; D019281:Dimerization; D004583:Electrons; D008958:Models, Molecular; D050607:Organogold Compounds / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism
chemical_list: D050607:Organogold Compounds