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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 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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Figure 1: Femtosecond time-resolved X-ray solution scattering at the XFEL facility and the data analysis.
Figure 2: Time-dependent structural changes of [Au(CN)2]3.
Figure 3: Structure determination of the S1 state using the experimental scattering curve at 200 fs time delay in momentum space and real space.
Figure 4: Mechanism of photoinduced bond formation in [Au(CN)2]3.

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References

  1. Zewail, A. H. Laser femtochemistry. Science 242, 1645–1653 (1988)

    Article  ADS  CAS  PubMed  Google Scholar 

  2. Harris, A. L., Brown, J. K. & Harris, C. B. The nature of simple photodissociation reactions in liquids on ultrafast time scales. Annu. Rev. Phys. Chem. 39, 341–366 (1988)

    Article  ADS  CAS  Google Scholar 

  3. Jonas, D. M., Bradforth, S. E., Passino, S. A. & Fleming, G. R. Femtosecond wavepacket spectroscopy: influence of temperature, wavelength, and pulse duration. J. Phys. Chem. 99, 2594–2608 (1995)

    Article  CAS  Google Scholar 

  4. Rawashdeh-Omary, M. A., Omary, M. A., Patterson, H. H. & Fackler, J. P. Excited-state interactions for [Au(CN)2]n and [Ag(CN)2]n oligomers in solution. Formation of luminescent gold-gold bonded excimers and exciplexes. J. Am. Chem. Soc. 123, 11237–11247 (2001)

    Article  CAS  PubMed  Google Scholar 

  5. Iwamura, M., Nozaki, K., Takeuchi, S. & Tahara, T. Real-time observation of tight Au–Au bond formation and relevant coherent motion upon photoexcitation of [Au(CN)2] oligomers. J. Am. Chem. Soc. 135, 538–541 (2013)

    Article  CAS  PubMed  Google Scholar 

  6. Cui, G. L., Cao, X. Y., Fang, W. H., Dolg, M. & Thiel, W. Photoinduced gold(I)-gold(I) chemical bonding in dicyanoaurate oligomers. Angew. Chem. Int. Ed. 52, 10281–10285 (2013)

    Article  CAS  Google Scholar 

  7. Tamasaku, K. et al. X-ray two-photon absorption competing against single and sequential multiphoton processes. Nature Photon. 8, 313–316 (2014)

    Article  ADS  CAS  Google Scholar 

  8. Rini, M., Magnes, B. Z., Pines, E. & Nibbering, E. T. J. Real-time observation of bimodal proton transfer in acid-base pairs in water. Science 301, 349–352 (2003)

    Article  ADS  CAS  PubMed  Google Scholar 

  9. Rosspeintner, A., Lang, B. & Vauthey, E. Ultrafast photochemistry in liquids. Annu. Rev. Phys. Chem. 64, 247–271 (2013)

    Article  ADS  CAS  PubMed  Google Scholar 

  10. Pyykkö, P. Theoretical chemistry of gold. Angew. Chem. Int. Ed. 43, 4412–4456 (2004)

    Article  Google Scholar 

  11. Wang, S. G. & Schwarz, W. H. E. Quasi-relativistic density functional study of aurophilic interactions. J. Am. Chem. Soc. 126, 1266–1276 (2004)

    Article  CAS  PubMed  Google Scholar 

  12. Schmidbaur, H. & Schier, A. A briefing on aurophilicity. Chem. Soc. Rev. 37, 1931–1951 (2008)

    Article  CAS  PubMed  Google Scholar 

  13. Ihee, H. Visualizing solution-phase reaction dynamics with time-resolved X-ray liquidography. Acc. Chem. Res. 42, 356–366 (2009)

    Article  CAS  PubMed  Google Scholar 

  14. Ihee, H. et al. Ultrafast X-ray diffraction of transient molecular structures in solution. Science 309, 1223–1227 (2005)

    Article  ADS  CAS  PubMed  Google Scholar 

  15. Davidsson, J. et al. Structural determination of a transient isomer of CH2I2 by picosecond x-ray diffraction. Phys. Rev. Lett. 94, 245503 (2005)

    Article  ADS  Google Scholar 

  16. Christensen, M. et al. Time-resolved X-ray scattering of an electronically excited state in solution. Structure of the 3A2u state of tetrakis-μ-pyrophosphitodiplatinate(II). J. Am. Chem. Soc. 131, 502–508 (2009)

    Article  CAS  PubMed  Google Scholar 

  17. Kim, K. H. et al. Solvent-dependent molecular structure of ionic species directly measured by ultrafast X-ray solution scattering. Phys. Rev. Lett. 110, 165505 (2013)

    Article  ADS  PubMed  Google Scholar 

  18. Plech, A., Kotaidis, V., Lorenc, M. & Boneberg, J. Femtosecond laser near-field ablation from gold nanoparticles. Nature Phys. 2, 44–47 (2006)

    Article  ADS  CAS  Google Scholar 

  19. Kim, K. H. et al. Direct observation of cooperative protein structural dynamics of homodimeric hemoglobin from 100 ps to 10 ms with pump-probe X-ray solution scattering. J. Am. Chem. Soc. 134, 7001–7008 (2012)

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  20. Sokolowski-Tinten, K. et al. Femtosecond X-ray measurement of coherent lattice vibrations near the Lindemann stability limit. Nature 422, 287–289 (2003)

    Article  ADS  CAS  PubMed  Google Scholar 

  21. Fritz, D. M. et al. Ultrafast bond softening in bismuth: mapping a solid’s interatomic potential with X-rays. Science 315, 633–636 (2007)

    Article  ADS  CAS  PubMed  Google Scholar 

  22. Coppens, P. Molecular excited-state structure by time-resolved pump-probe X-ray diffraction. What is new and what are the prospects for further progress? J. Phys. Chem. Lett. 2, 616–621 (2011)

    Article  CAS  Google Scholar 

  23. Miller, T. A. et al. The mechanism of ultrafast structural switching in superionic copper(I) sulphide nanocrystals. Nature Commun. 4, 1369 (2013)

    Article  ADS  CAS  Google Scholar 

  24. Zewail, A. H. Four-dimensional electron microscopy. Science 328, 187–193 (2010)

    Article  ADS  CAS  PubMed  Google Scholar 

  25. Kirchner, F. O., Gliserin, A., Krausz, F. & Baum, P. Laser streaking of free electrons at 25 keV. Nature Photon. 8, 52–57 (2014)

    Article  ADS  CAS  Google Scholar 

  26. Miller, R. J. D. Mapping atomic motions with ultrabright electrons: the chemists’ gedanken experiment enters the lab frame. Annu. Rev. Phys. Chem. 65, 583–604 (2014)

    Article  ADS  CAS  PubMed  Google Scholar 

  27. Bressler, C. et al. Femtosecond XANES study of the light-induced spin crossover dynamics in an iron(II) complex. Science 323, 489–492 (2009)

    Article  ADS  CAS  PubMed  Google Scholar 

  28. Lemke, H. T. et al. Femtosecond X-ray absorption spectroscopy at a hard X-ray free electron laser: application to spin crossover dynamics. J. Phys. Chem. A 117, 735–740 (2013)

    Article  CAS  PubMed  Google Scholar 

  29. Zhang, W. et al. Tracking excited-state charge and spin dynamics in iron coordination complexes. Nature 509, 345–348 (2014)

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  30. Arnlund, D. et al. Visualizing a protein quake with time-resolved X-ray scattering at a free-electron laser. Nature Methods 11, 923–926 (2014)

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  31. Inubushi, Y. et al. Determination of the pulse duration of an X-ray free electron laser using highly resolved single-shot spectra. Phys. Rev. Lett. 109, 144801 (2012)

    Article  ADS  PubMed  Google Scholar 

  32. Ishikawa, T. et al. A compact X-ray free-electron laser emitting in the sub-angstrom region. Nature Photon. 6, 540–544 (2012)

    Article  ADS  CAS  Google Scholar 

  33. Rawashdeh-Omary, M. A., Omary, M. A. & Patterson, H. H. Oligomerization of Au(CN)2 and Ag(CN)2 ions in solution via ground-state aurophilic and argentophilic bonding. J. Am. Chem. Soc. 122, 10371–10380 (2000)

    Article  CAS  Google Scholar 

  34. Kim, T. K., Lee, J. H., Wulff, M., Kong, Q. Y. & Ihee, H. Spatiotemporal kinetics in solution studied by time-resolved X-ray liquidography (solution scattering). ChemPhysChem 10, 1958–1980 (2009)

    Article  CAS  PubMed  Google Scholar 

  35. Ichiyanagi, K. et al. 100 ps time-resolved solution scattering utilizing a wide-bandwidth X-ray beam from multilayer optics. J. Synchrotron Radiat. 16, 391–394 (2009)

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  36. Haldrup, K. et al. Structural tracking of a bimolecular reaction in solution by time-resolved X-ray scattering. Angew. Chem. Int. Ed. 48, 4180–4184 (2009)

    Article  CAS  Google Scholar 

  37. Jun, S. et al. Photochemistry of HgBr2 in methanol investigated using time-resolved X-ray liquidography. Phys. Chem. Chem. Phys. 12, 11536–11547 (2010)

    Article  CAS  PubMed  Google Scholar 

Download references

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).

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Authors and Affiliations

Authors

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.

Corresponding author

Correspondence to Hyotcherl Ihee.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Comparison of the TRXSS signals at SACLA and KEK and the TRXSS data in the entire time range.

a, Comparison of the difference scattering curves at 100 ps time delay measured at SACLA (black) and KEK (red). The error bar at each data point indicates the standard error determined from 50 independent measurements. The two curves are nearly identical to each other within the experimental error, indicating that the difference scattering curves are highly reproducible and independent of the facility. b, Experimental difference scattering curves, qΔS(qt), in the entire time range from –800 fs to 1 μs.

Extended Data Figure 2 Solvent heating contribution to the TRXSS signal.

a, Experimental difference scattering curves, qΔS(q), of FeCl3 solution measured at several time delays (400 fs, 1.9 ps, 3.9 ps, 5.9 ps, 7.9 ps, 30 ps and 100 ps). b, SVD of the experimental difference scattering curves of FeCl3 measured from –10 ps to 100 ps. The first two right singular vectors multiplied by singular values are shown. c, The first right singular vector (black circles) fitted by an error function (red curve). This result implies that only a single difference scattering curve accounts for solvent heating in the time range up to 100 ps. d, Comparison of the difference scattering curve of the [Au(CN)2]3 solution at 1 μs time delay (black) and the difference scattering curve for solvent heating (red). The error bar at each data point indicates the standard error determined from 50 independent measurements. At this time delay, the two curves are almost identical to each other within the experimental error, confirming that the difference scattering at late time delays are dominated by the solvent heating.

Extended Data Figure 3 Difference RDFs in real space.

Difference RDFs, r2ΔS(r), obtained by Fourier sine transformation of qΔS(q).

Extended Data Figure 4 Species-associated difference RDFs of the transient states.

The species-associated difference RDFs of the S0, S1, T1 and tetramer states correspond to , , and , respectively. We used a common S0 structure when fitting all four species-associated difference RDFs. By optimizing the fit between the theoretical and the experimental difference RDFs for each transient species via the structural fitting analysis, we were able to obtain the theoretical RDF of the S0 state.

Extended Data Figure 5 Radial distribution functions, r2S(rt).

The RDF of the S0 state was added to the RDFs at all time delays to emphasize only the contributions of the transient solute species associated with the bond formation.

Extended Data Figure 6 Comparison of the scattering from Au atoms and other contributions.

a, Because the scattering intensities from C and N atoms are negligibly small, the total scattering pattern is almost the same as the scattering from Au atoms only. b, The contribution of the cage term is small and the total scattering pattern is therefore almost the same as the solute-only term.

Extended Data Figure 7 Contributions of trimer and dimer to X-ray scattering signal.

a, Concentrations of the three species [Au], [Au2] and [Au3], calculated as a function of c, which is the initial concentration of monomers of the gold complex. We assumed that K2 is 10 M–2 in this case. b, Absorption spectra of aqueous solutions of K[Au(CN)2] at various concentrations measured with a 0.5 mm path length cell. Four points (A1, A2, A3 and A4) that are used as inputs are indicated. c, Theoretical difference scattering curves for the trimer (black) and the dimer (red). Relative intensities of the two curves were estimated realistically based on the excitation probabilities and the equilibrium of the two species.

Extended Data Figure 8 Comparison of the TRXSS data measured with excitations at two different wavelengths, 310 and 267 nm.

a, Right singular vectors obtained from the SVD analysis for the 310 nm (left) and 267 nm (right) excitations. For both cases, the right singular vectors were fitted by only one kinetic component and their extracted time constants are almost identical to each other. b, Difference scattering curves at 100 ps time delay measured with excitations at 310 nm (black) and 267 nm (red). The error bar at each data point indicates the standard error determined from 50 independent measurements. The two curves are identical to each other within the experimental error. This similarity between the kinetics and the shapes of the difference scattering curves indicates negligible contribution from dimer excitation for both 310 and 267 nm excitations.

Extended Data Figure 9 Mechanism of photoinduced bond formation in [Au(CN)2]3. Results from our TRXSS data (red) and the previous transient absorption experiment (blue) are shown together.

Our findings are in good agreement with the reaction mechanism proposed in the transient absorption study, except for the structural assignments of the early kinetics. Considering that TRXSS is sensitive only to the processes accompanying structural change, the intersystem crossing processes on 500 fs and 13 ns timescales, which were not observed in the TRXSS measurement, are likely to involve no structural change.

Extended Data Figure 10 Species-associated RDFs of the four structures obtained from the SVD and principal-component analyses (black) and their fits (red) obtained by using the Debye–Waller factor and the constraint of the symmetric structure for the S0 state.

For each state, the structural parameters obtained from the fits and their standard errors determined from 50 independent measurements are shown together. It can be seen that the structural parameters of S1, T1 and the tetramer obtained from the fits using the Debye–Waller factor and the symmetric constraint for S0 are similar to the values given in Fig. 2d.

Extended Data Table 1 Details of the data-collection parameters

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Kim, K., Kim, J., Nozawa, S. et al. Direct observation of bond formation in solution with femtosecond X-ray scattering. Nature 518, 385–389 (2015). https://doi.org/10.1038/nature14163

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