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Published on: August 12, 2019
Solution NMR studies of iron(II) spin-crossover complexes
1Department of Chemistry and Biochemistry, Ludwig Maximilian University Munich, Butenandtstrasse 5-13 (Haus D), München, Germany. bwmch@cup.uni-muenchen.de
Inorganic Chemistry
|July 17, 2007
Summary
Proton NMR spectroscopy effectively tracks iron spin transitions in solution for pyridine complexes. This method complements magnetic susceptibility measurements, revealing cooperative effects in dinuclear iron complexes.
Area of Science:
- Coordination Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- Investigated mono- and dinuclear pyridine iron complexes with Schiff base ligands.
- Ligands were synthesized via condensation reactions.
- Complexes feature N2O22- coordination spheres around iron centers.
Purpose of the Study:
- To investigate the 1H NMR spectra of novel iron(II) pyridine complexes in solution.
- To correlate NMR spectral shifts with the spin state of the iron centers.
- To compare solution-phase spin-transition behavior with solid-state data.
Main Methods:
- Synthesis of mono- and dinuclear iron(II) complexes with Schiff base ligands.
- 1H NMR spectroscopy in mixed toluene-d8/pyridine-d5 solutions across a temperature range (188-358 K).
- Magnetic susceptibility measurements using the Evans method in solution.
Main Results:
- 1H NMR shifts strongly correlate with the spin state of the iron center.
- High-spin iron(II) complexes exhibit Curie-like behavior.
- NMR shift analysis accurately determines the high-spin mole fraction in solution.
- Solution spin-transition behavior differs from solid-state, but NMR and Evans method data align.
- Isotropic shifts are suitable for monitoring spin transitions in solution.
- Dinuclear complexes show slight differences in transition steepness, suggesting cooperativity.
Conclusions:
- 1H NMR spectroscopy is a valuable tool for studying spin transitions in solution.
- NMR data provides insights into the high-spin mole fraction and cooperative effects.
- Solution-phase studies reveal nuances not apparent in solid-state analyses.
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