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 techniques1,2,3, 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 state4,5,6, 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 lasers7 and advanced analysis of time-resolved solution scattering data.

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Acknowledgements

We thank M. Iwamura and K. Nozaki for discussions. This work was supported by IBS-R004-G2; the X-ray Free Electron Laser Priority Strategic Program of MEXT, Japan; PRESTO/JST; the Innovative Areas ‘Artificial Photosynthesis (AnApple)’ (no. 25107527) grant from the Japan Society for the Promotion of Science; and the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Science, ICT & Future Planning (NRF-2014R1A1A1002511). The experiments were performed at beamline BL3 of SACLA with the approval of the Japan Synchrotron Radiation Research Institute (proposal nos 2012A8030, 2012A8038, 2012B8029, 2012B8043, 2013A8053, 2013B8036, 2013B8059, 2014A8042 and 2014A8022) and at beamline NW14A of KEK with the approval of the Photon Factory Program Advisory Committee (proposal nos 2011G655, 2012G778 and 2012G779).

Author information

Author notes

    • Kyung Hwan Kim
    • , Jong Goo Kim
    • , Shunsuke Nozawa
    •  & Tokushi Sato

    These authors contributed equally to this work.

    • Tokushi Sato
    • , Takahiro Sato
    •  & Kanade Ogawa

    Present addresses: Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22607 Hamburg, Germany (Tokushi Sato); Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan (Takahiro Sato); Japan Atomic Energy Agency, 8-1-7 Umemidai, Kizugawa, Kyoto 619-0215, Japan (K.O.).

Affiliations

  1. Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea

    • Kyung Hwan Kim
    • , Jong Goo Kim
    • , Key Young Oang
    • , Tae Wu Kim
    • , Hosung Ki
    • , Junbeom Jo
    • , Sungjun Park
    • , Ryong Ryoo
    •  & Hyotcherl Ihee
  2. Department of Chemistry, KAIST, Daejeon 305-701, South Korea

    • Kyung Hwan Kim
    • , Jong Goo Kim
    • , Key Young Oang
    • , Tae Wu Kim
    • , Hosung Ki
    • , Junbeom Jo
    • , Sungjun Park
    • , Ryong Ryoo
    •  & Hyotcherl Ihee
  3. Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan

    • Shunsuke Nozawa
    • , Tokushi Sato
    •  & Shin-ichi Adachi
  4. RIKEN SPring-8 Center, Kouto 1-1-1, Sayo, Hyogo 679-5148, Japan

    • Changyong Song
    • , Takahiro Sato
    • , Kanade Ogawa
    • , Makina Yabashi
    •  & Tetsuya Ishikawa
  5. Japan Synchrotron Radiation Research Institute, Kouto 1-1-1, Sayo, Hyogo 679-5198, Japan

    • Tadashi Togashi
    •  & Kensuke Tono
  6. Department of Chemistry, The Catholic University of Korea, Bucheon 420-743, South Korea

    • Joonghan Kim
  7. Department of Chemistry, Inha University, Incheon 402-751, South Korea

    • Jeongho Kim
  8. 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

    • Shin-ichi Adachi

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Contributions

H.I. and S.-i.A. designed the study. K.H.K., J.G.K., S.N., Tokushi Sato, K.Y.O., T.W.K., H.K., J.J., S.P., C.S., Takahiro Sato, K.O., T.T., K.T., M.Y., T.I., Jeongho Kim, H.I. and S.-i.A. did the experiment. K.H.K., J.G.K., S.N., Tokushi Sato and Joonghan Kim analysed the data. K.H.K., J.G.K., S.N., K.Y.O., R.R., Jeongho Kim, H.I. and S.-i.A. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Hyotcherl Ihee.

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DOI

https://doi.org/10.1038/nature14163

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