title: Direct observation of bond formation in solution with femtosecond X-ray scattering.
abstract: The making and breaking of atomic bonds are essential processes in chemical reactions. Although the ultrafast dynamics of bond breaking have been studied intensively using time-resolved techniques, it is very difficult to study the structural dynamics of bond making, mainly because of its bimolecular nature. It is especially difficult to initiate and follow diffusion-limited bond formation in solution with ultrahigh time resolution. Here we use femtosecond time-resolved X-ray solution scattering to visualize the formation of a gold trimer complex, [Au(CN)2(-)]3 in real time without the limitation imposed by slow diffusion. This photoexcited gold trimer, which has weakly bound gold atoms in the ground state, undergoes a sequence of structural changes, and our experiments probe the dynamics of individual reaction steps, including covalent bond formation, the bent-to-linear transition, bond contraction and tetramer formation with a time resolution of ∼500 femtoseconds. We also determined the three-dimensional structures of reaction intermediates with sub-ångström spatial resolution. This work demonstrates that it is possible to track in detail and in real time the structural changes that occur during a chemical reaction in solution using X-ray free-electron lasers and advanced analysis of time-resolved solution scattering data.
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Kim
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Jong Goo
authors.initials: JG
authors.lastname: Kim
authors.affiliation: Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Nozawa
authors.affiliation: Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Tokushi
authors.initials: T
authors.lastname: Sato
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Key Young
authors.initials: KY
authors.lastname: Oang
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Tae Wu
authors.initials: TW
authors.lastname: Kim
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Hosung
authors.initials: H
authors.lastname: Ki
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Junbeom
authors.initials: J
authors.lastname: Jo
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Sungjun
authors.initials: S
authors.lastname: Park
authors.affiliation: RIKEN SPring-8 Center, Kouto 1-1-1, Sayo, Hyogo 679-5148, Japan.
authors.forename: Changyong
authors.initials: C
authors.lastname: Song
authors.affiliation: RIKEN SPring-8 Center, Kouto 1-1-1, Sayo, Hyogo 679-5148, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sato
authors.affiliation: RIKEN SPring-8 Center, Kouto 1-1-1, Sayo, Hyogo 679-5148, Japan.
authors.forename: Kanade
authors.initials: K
authors.lastname: Ogawa
authors.affiliation: Japan Synchrotron Radiation Research Institute, Kouto 1-1-1, Sayo, Hyogo 679-5198, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Togashi
authors.affiliation: Japan Synchrotron Radiation Research Institute, Kouto 1-1-1, Sayo, Hyogo 679-5198, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Tono
authors.affiliation: RIKEN SPring-8 Center, Kouto 1-1-1, Sayo, Hyogo 679-5148, Japan.
authors.forename: Makina
authors.initials: M
authors.lastname: Yabashi
authors.affiliation: RIKEN SPring-8 Center, Kouto 1-1-1, Sayo, Hyogo 679-5148, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Department of Chemistry, The Catholic University of Korea, Bucheon 420-743, South Korea.
authors.forename: Joonghan
authors.initials: J
authors.lastname: Kim
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Ryong
authors.initials: R
authors.lastname: Ryoo
authors.affiliation: Department of Chemistry, Inha University, Incheon 402-751, South Korea.
authors.forename: Jeongho
authors.initials: J
authors.lastname: Kim
authors.affiliation: 1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea.
authors.forename: Hyotcherl
authors.initials: H
authors.lastname: Ihee
authors.affiliation: 1] Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan [2] Department of Materials Structure Science, School of High Energy Accelerator Science, The Graduate University for Advanced Studies, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Adachi