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A mononuclear Fe(III) single molecule magnet with a 3/2↔5/2 spin crossover
Susanne Mossin1, Ba L Tran, Debashis Adhikari
1Center for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark, 2800 Lyngby, Denmark. slmo@kemi.dtu.dk
Journal of the American Chemical Society
|July 24, 2012
Summary
This study reveals an iron complex exhibiting an unexpected spin transition from S = 3/2 to S = 5/2 above 80 K. This behavior indicates it functions as a single molecular magnet with a defined energy barrier.
Area of Science:
- Inorganic Chemistry
- Materials Science
- Magnetochemistry
Background:
- The synthesis and characterization of novel iron complexes are crucial for developing advanced magnetic materials.
- Understanding spin transitions in transition metal complexes is key to designing molecular magnets with tunable properties.
Purpose of the Study:
- To investigate the magnetic properties and spin state transitions of the air-stable iron complex [(PNP)FeCl(2)] (1).
- To elucidate the structural and electronic factors governing the observed spin crossover behavior.
Main Methods:
- Magnetic susceptibility measurements using dc and ac SQUID magnetometry.
- Variable-temperature Mössbauer spectroscopy and X-band Electron Paramagnetic Resonance (EPR) spectroscopy.
- Multiedge X-ray absorption spectroscopy (XAS) and variable-temperature single-crystal X-ray diffraction.
Main Results:
- Complex 1 exhibits an unexpected spin transition from S = 3/2 to S = 5/2 above 80 K.
- AC SQUID data confirm single molecular magnet behavior with a thermally activated barrier (U(eff) = 32-36 cm(-1)).
- Structural and spectroscopic data correlate the spin transition with changes in iron coordination geometry and electronic structure.
Conclusions:
- The iron complex [(PNP)FeCl(2)] demonstrates a temperature-induced spin crossover, functioning as a single molecular magnet.
- The observed spin transition is attributed to the proximity of quartet and sextet electronic states, influenced by ligand interactions and geometry.
- This work provides insights into the design principles for molecular magnetic materials based on iron complexes.
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