title: Hierarchy of bond stiffnesses within icosahedral-based gold clusters protected by thiolates.
abstract: Unique thermal properties of metal clusters are believed to originate from the hierarchy of the bonding. However, an atomic-level understanding of how the bond stiffnesses are affected by the atomic packing of a metal cluster and the interfacial structure with the surrounding environment has not been attained to date. Here we elucidate the hierarchy in the bond stiffness in thiolate-protected, icosahedral-based gold clusters Au25(SC2H4Ph)18, Au38(SC2H4Ph)24 and Au144(SC2H4Ph)60 by analysing Au L3-edge extended X-ray absorption fine structure data. The Au-Au bonds have different stiffnesses depending on their lengths. The long Au-Au bonds, which are more flexible than those in the bulk metal, are located at the icosahedral-based gold core surface. The short Au-Au bonds, which are stiffer than those in the bulk metal, are mainly distributed along the radial direction and form a cyclic structural backbone with the rigid Au-SR oligomers.
authors.affiliation: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.|Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto 615-8520, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Yamazoe
authors.affiliation: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Takano
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Kurashige
authors.affiliation: Department of Materials Molecular Science, Institute for Molecular Science, Myodaiji, Okazaki, Aichi 444-8585, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yokoyama
authors.affiliation: Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1 Koto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Kiyofumi
authors.initials: K
authors.lastname: Nitta
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Negishi
authors.affiliation: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.|Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto 615-8520, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tsukuda