Locking and Unlocking of the Molecular Spin Crossover Transition

ORAL

Abstract

The electronic state of Fe(II) spin crossover complex [Fe{H2B(pz)2}2(bipy)] (pz = pyrazol-1-yl, bipy = 2,2′-bipyridine) has been investigated by X-ray absorption spectroscopy (XAS). Locking in a largely low-spin-state configuration over a temperature range that includes temperatures well above the thermal spin crossover temperature of 160 K, to well above room temperature, has been found in both nanometer thin films (by substrate interactions) and powder (by mixing with strongly dipolar zwitterions). The XAS clearly shows the change of iron L2 edge spectra, typically associated with thermal induced spin crossover. Remarkably, incident X-ray fluences then restore the complex moiety to a high spin state at temperatures of 200 K to above room temperature, well above the spin crossover transition temperature for the pristine powder, and this is an activated process, as will be discussed in this presentation. Relaxation back to the initial locked state can be accomplished by heating slightly above room temperature.

*Funded by NSF.

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Presenters

  • Guanhua Hao

    • Physics and Astronomy, University of Nebraska-Lincoln

Authors

  • Guanhua Hao

    • Physics and Astronomy, University of Nebraska-Lincoln

  • Xin Zhang

    • Physics and Astronomy, University of Nebraska-Lincoln

  • Paulo Costa

    • Physics and Astronomy, University of Nebraska-Lincoln

  • James Hooper

    • Department of Theoretical Chemistry, Jagiellonian University

  • Daniel Miller

    • Department of Chemistry, University of Buffalo

  • Alpha N'Diaye

    • Lawrence Berkeley National Laboratory
    • Lawrence Berkeley Natl Lab
    • Advanced Light Source
    • Advanced Light Source, Lawrence Berkeley National Laboratory

  • Xuanyuan Jiang

    • Physics and Astronomy, Univ of Nebraska - Lincoln
    • Univ of Nebraska - Lincoln
    • Physics and Astronomy, University of Nebraska-Lincoln

  • Yuewei Yin

    • Physics and Astronomy, University of Nebraska-Lincoln
    • Penn State Univ

  • Lucie Routaboul

    • Department of Chemistry, Université de Strasbourg

  • Pierre Braunstein

    • Department of Chemistry, Université de Strasbourg

  • Xiaoshan Xu

    • Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln
    • Physics and Astronomy, Univ of Nebraska - Lincoln
    • Univ of Nebraska - Lincoln
    • University of Nebraska-Lincoln
    • Physics and Astronomy, University of Nebraska-Lincoln

  • Axel Enders

    • Physikalisches Institut, Universität Bayreuth
    • Physikalisches Institut, Universitat Bayreuth

  • Eva Zurek

    • Department of Chemistry, State University of New York at Buffalo
    • Department of Chemistry, University of Buffalo

  • Peter Dowben

    • Univ of Nebraska - Lincoln
    • Physics and Astronomy, University of Nebraska-Lincoln
    • Department of Physics and Astronomy, University of Nebraska-Lincoln