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Structures of Fe(II) spin-crossover complexes from synchrotron powder-diffraction data
Eva Dova1, René Peschar, Makoto Sakata
1University of Amsterdam, Faculty of Science, van 't Hoff Institute for Molecular Sciences, Laboratory for Crystallography, Nieuwe Achtergracht 166, NL-1018 WV Amsterdam, The Netherlands. eva@science.uva.nl
Acta Crystallographica. Section B, Structural Science
|September 16, 2004
Summary
This study determined the crystal structures of two spin-crossover compounds, teei and teeb, at high- and low-spin states. Gradual spin-crossover events in these iron complexes likely involve minimal structural changes.
Area of Science:
- Inorganic Chemistry
- Solid-State Chemistry
- Crystallography
Background:
- Spin-crossover (SCO) compounds are coordination complexes exhibiting a reversible switch between low-spin and high-spin states.
- Understanding the structural changes associated with SCO is crucial for designing functional materials.
Purpose of the Study:
- To determine the crystal structures of two iron(II) spin-crossover compounds, [Fe(teeI)(6)](BF4)2 (teei) and [Fe(teeBr)(6)](BF4)2 (teeb).
- To analyze the structural differences between the high-spin and low-spin states of these SCO compounds.
Main Methods:
- High-resolution synchrotron powder diffraction data collection at ESRF and SPring8.
- Direct-space structure determination techniques (grid search, genetic algorithm, parallel tempering) for teei.
- Rietveld refinement with geometrical restraints.
- Analysis of diffraction data and structural parameters.
Main Results:
- Crystal structures of teei in both high-spin (near 300 K) and low-spin (90 K) states were successfully determined.
- A structural model for teeb was obtained, but full refinement was hindered by an amorphous component.
- Both compounds crystallize in space group P2(1)/c with Z=2.
- Analysis revealed overall structural similarity between the compounds and their spin states.
Conclusions:
- The gradual spin-crossover behavior in teei and teeb is likely associated with only minor structural modifications.
- The absence of significant phase transitions suggests continuous structural changes during the spin transition.