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Dynamics of BF 4 - anion reorientation in the spin-crossover compound [Fe(1-n-propyl-1H-tetrazole) 6 ](BF 4 ) 2 and in its Zn II analogue

  • M. Bokor
  • T. Marek
  • K. Tompa
  • P. Gütlich
  • A. Vértes

Abstract:

19 F and 11 B spin-lattice relaxation times were measured in [Zn(ptz) 6 ] (BF 4 ) 2 \(\) and in the spin-crossover compound [Fe(ptz) 6 ] (BF 4 ) 2 . For both compounds BF 4 - anion reorientation is active above 50 K. For [Zn(ptz) 6 ] (BF 4 ) 2 , the anion-reorientation dynamics is different in the temperature regions of 50-90 K, 90-120 K, and above 150 K; between 120 and 150 K it changes rapidly reflecting a structural change. In [Fe(ptz) 6 ] (BF 4 ) 2 the mechanism for the paramagnetic relaxation involving the 19 F nuclei is found to be of the diffusion-limited type according to the theory of Lowe and Tse. The present results prove that the spin-crossover takes place in a dynamic surrounding and not in a static crystal lattice.

PACS. 33.15.Vb Correlation times in molecular dynamics - 33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics) - 33.25.+k Nuclear resonance and relaxation 

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Copyright information

© EDP Sciences, Springer-Verlag, Società Italiana di Fisica 1999

Authors and Affiliations

  • M. Bokor
    • 1
  • T. Marek
    • 1
  • K. Tompa
    • 1
  • P. Gütlich
    • 3
  • A. Vértes
    • 2
  1. 1.Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, pob. 49, 1525 Budapest, HungaryHU
  2. 2.Department of Nuclear Chemistry, Eötvös University, Budapest, HungaryHU
  3. 3.Institut für Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg-Universität Mainz, GermanyDE

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