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Structural phase transition to disorder low-temperature phase in [Fe(ptz)6](BF4)2 spin-crossover compounds
Joachim Kusz1, Maciej Zubko, Reinhard B Neder
1Institute of Physics, University of Silesia, ul. Uniwersytecka 4, PL-40007 Katowice, Poland. kusz@us.edu.pl
Acta Crystallographica. Section B, Structural Science
|January 24, 2012
Summary
Spin-crossover compound [Fe(ptz)6](BF4)2 exhibits six phases. Slow cooling induces a reversible disordered phase with layered domains, distinct from rapidly cooled samples.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Crystallography
Background:
- Spin-crossover (SCO) compounds, such as [Fe(ptz)6](BF4)2, display distinct electronic and structural properties.
- Understanding phase transitions in SCO materials is crucial for their application in molecular devices.
Purpose of the Study:
- To investigate the structural changes and disorder in the spin-crossover compound [Fe(ptz)6](BF4)2 upon cooling.
- To elucidate the nature of the disordered phase and its relationship to the ordered low-spin phase.
Main Methods:
- Single-crystal X-ray diffraction
- Analysis of diffuse and satellite reflections
- Structure refinement in non-standard space groups
Main Results:
- Slow cooling below 125 K leads to a reversible disordered phase characterized by diffuse maxima along c* and additional satellite reflections.
- The disordered phase exhibits short-range order along c and long-range order in the ab plane, with layered domains shifted in the hexagonal ab plane.
- Structure solution in the non-standard space group C1 revealed a non-centrosymmetric coordination polyhedron for the Fe ion and altered conformations of propyl groups.
Conclusions:
- The study reveals a novel disordered phase in [Fe(ptz)6](BF4)2, distinct from the R3bar symmetry observed in rapidly cooled samples.
- The findings provide insights into the complex phase behavior of spin-crossover materials and the structural basis of disorder.
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