title: Understanding Ligand-Exchange Reactions on Thiolate-Protected Gold Clusters by Probing Isomer Distributions Using Reversed-Phase High-Performance Liquid Chromatography.
abstract: Thiolate-protected gold clusters (Aun(SR)m) have attracted considerable attention as functional nanomaterials in a wide range of fields. A ligand-exchange reaction has long been used to functionalize these clusters. In this study, we separated products from a ligand-exchange reaction of phenylethanethiolate-protected Au24Pd clusters (Au24Pd(SC2H4Ph)18), in which Au25(SR)18 is doped with palladium, into each coordination isomer with high resolution by reversed-phase high-performance liquid chromatography. This success has enabled isomer distributions of the products to be quantitatively evaluated. We evaluated quantitatively the isomer distributions of products obtained by the reaction of Au24Pd(SC2H4Ph)18 with thiol, disulfide, or diselenide. The results revealed that the exchange reaction starts to occur preferentially at thiolates that are bound directly to the metal core (thiolates of a core site) in all reactions. Further study on the isomer-separated Au24Pd(SC2H4Ph)17(SC12H25) revealed that clusters vary the coordination isomer distribution in solution by the ligand-exchange reaction between clusters and that control of the coordination isomer distribution of the starting clusters enables control of the coordination isomer distribution of the products generated by ligand-exchange reactions between clusters. Au24Pd(SC2H4Ph)18 used in this study has a similar framework structure to Au25(SR)18, which is one of the most studied compounds in the Aun(SR)m clusters. Knowledge gained in this study is expected to enable further understanding of ligand-exchange reactions on Au25(SR)18 and other Aun(SR)m clusters.
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science , 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Niihori
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science , 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kikuchi
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science , 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
authors.forename: Ayano
authors.initials: A
authors.lastname: Kato
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science , 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
authors.forename: Miku
authors.initials: M
authors.lastname: Matsuzaki
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science , 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.|Photocatalysis International Research Center, Tokyo University of Science , 2641 Yamazaki, Noda, Chiba 278-8510, Japan.|Department of Materials Molecular Science, Institute for Molecular Science , Myodaiji, Okazaki, Aichi 444-8585, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Negishi
keywords: coordination isomer; isomer distribution; ligand-exchange reaction; reversed-phase high-performance liquid chromatography; thiolate-protected gold clusters