Abstract

The entatic state denotes a distorted coordination geometry of a complex from its typical arrangement that generates an improvement to its function. The entatic-state principle has been observed to apply to copper electron-transfer proteins and it results in a lowering of the reorganization energy of the electron-transfer process. It is thus crucial for a multitude of biochemical processes, but its importance to photoactive complexes is unexplored. Here we study a copper complex—with a specifically designed constraining ligand geometry—that exhibits metal-to-ligand charge-transfer state lifetimes that are very short. The guanidine–quinoline ligand used here acts on the bis(chelated) copper(I) centre, allowing only small structural changes after photoexcitation that result in very fast structural dynamics. The data were collected using a multimethod approach that featured time-resolved ultraviolet–visible, infrared and X-ray absorption and optical emission spectroscopy. Through supporting density functional calculations, we deliver a detailed picture of the structural dynamics in the picosecond-to-nanosecond time range.

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Acknowledgements

S.H.-P. acknowledges generous funding by the Deutsche Forschungsgemeinschaft (FOR1405 and SFB749, project B10) and M.R. thanks the Bundesministerium für Bildung und Forschung (BMBF VUV-FAST/05K2014 and 05K12GU1) and DFG (FOR1405). Also, W.Z. thanks the SFB749 (project A5) and the Cluster of Excellence ‘Munich-Center for Advanced Photonics’ and ‘Center for Integrated Protein Science (CIPSM)’. This work was supported by the project ELI (Extreme Light Infrastructure) phase 2 (CZ.02.1.01/0.0/0.0/15_008/0000162) from the European Regional Development Fund. J.A. acknowledges funding from the Röntgen Ångström Cluster and the Chalmers Area of Advance Materials Science. C.B. is grateful for funding by the European XFEL, the DFG via SFB925 (TP A4) and the Centre for Ultrafast Imaging. Parts of this research were carried out at beamline P11 at the PETRA III storage ring at DESY, a member of the Helmholtz Association. We thank the DESY beamline scientists B. Reime, A. Burkhardt, S. Panneerselvam and O. Lorbeer for their support. Moreover, we thank the XFEL team members C. Youngman, P. Gessler, A. Beckmann and A. Galler for the efficient integration of the MHz digitizer into our X-ray setup at P11.

Author information

Affiliations

  1. Institute of Nanostructure and Solid State Physics, University of Hamburg, 22761 Hamburg, Germany

    • B. Dicke
    • , B. Grimm-Lebsanft
    • , F. Biebl
    • , D. Rukser
    • , M. Naumova
    • , M. Biednov
    • , G. Neuber
    • , A. Wetzel
    •  & M. Rübhausen
  2. Center for Free-Electron Laser Science (CFEL), Luruper Chaussee 149, 22761 Hamburg, Germany

    • B. Dicke
    • , B. Grimm-Lebsanft
    • , F. Biebl
    • , D. Rukser
    • , M. Biednov
    • , G. Neuber
    • , A. Wetzel
    • , K. R. Beyerlein
    • , H. N. Chapman
    •  & M. Rübhausen
  3. Institute for Inorganic Chemistry, RWTH Aachen University, 52074 Aachen, Germany

    • A. Hoffmann
    • , J. Stanek
    •  & S. Herres-Pawlis
  4. Institute for BioMolecular Optics and Center for Integrated Protein Science (CIPSM), Ludwig-Maximilians-Universität Munich, Oettingenstraße 67, 80538 Munich, Germany

    • M. S. Rampp
    • , B. Maerz
    • , S. M. Hofmann
    •  & W. Zinth
  5. Deutsches Elektronensynchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany

    • D. Göries
    • , P. Roedig
    • , A. Meents
    •  & H. N. Chapman
  6. Department of Chemistry, University of Paderborn, 33098 Paderborn, Germany

    • M. Naumova
  7. Laboratory of Molecular Biophysics, Department of Cell and Molecular Biology, Uppsala University, Husargatan 3 (Box 596), SE-751 24 Uppsala, Sweden

    • J. Bielecki
    •  & J. Andreasson
  8. European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany

    • J. Bielecki
    •  & C. Bressler
  9. ELI Beamlines, Institute of Physics, Czech Academy of Science, Na Slovance 2, 182 21 Prague, Czech Republic

    • J. Andreasson
  10. Condensed Matter Physics, Department of Physics, Chalmers University of Technology, Göteborg, Sweden

    • J. Andreasson
  11. Department of Physics, Technical University of Denmark, Fysikvej 307, Kongens Lyngby 2800, Denmark

    • C. Bressler
  12. The Hamburg Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany

    • C. Bressler

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Contributions

B.D., M.N., M.B., B.G.-L., S.H.-P., A.H., J.S., D.R., A.W. and J.B. performed the transient XAS measurements under the supervision of M.R.; the set-up for the transient XAS measurements was designed and developed by D.G., B.D., P.R. and A.M.; A.M., C.B., B.D., D.G., S.H.-P. and M.R. contributed to the improved data-acquisition technique; B.D. and M.N. analysed the transient XAS data; B.G.-L. performed the time-resolved optical emission experiments under the supervision of M.R.; J.A., F.B., H.N.C., K.R.B. and G.N. participated in the discussions about the data; A.H. and J.S. prepared the samples and A.H. performed the DFT calculations; the interpretation of the theoretical data in relation to the diverse experimental data was done by A.H. and S.H.-P.; M.S.R. and S.M.H. performed the transient infrared measurements under the supervision of W.Z.; B.M. accomplished the transient UV/vis measurements under the supervision of W.Z.; the interpretation of the entire experimental optical and XAS data was delivered by C.B., M.R., S.H.-P. and W.Z.; S.H.-P., W.Z. and M.R. designed the study and wrote the manuscript together with C.B., A.H. and B.D.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to W. Zinth or M. Rübhausen or S. Herres-Pawlis.

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https://doi.org/10.1038/nchem.2916