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Heteroleptic iron(ii) complexes with naphthoquinone-type ligands
Takuya Shiga1, Rina Kumamaru, Graham N Newton
1Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8571, Japan. shiga@chem.tsukuba.ac.jp.
Dalton Transactions (Cambridge, England : 2003)
|January 10, 2020
Summary
New iron complexes featuring a naphthoquinone ligand exhibit tunable spin-crossover properties. Researchers explored their magnetic behavior, revealing distinct low-spin and high-spin states based on ligand variations.
Area of Science:
- Coordination Chemistry
- Materials Science
- Magnetochemistry
Background:
- Iron complexes are crucial in catalysis and materials science.
- Spin-crossover (SCO) phenomena in iron complexes offer potential for molecular switches and sensors.
- Naphthoquinone-based ligands provide unique electronic and structural properties for metal complex design.
Purpose of the Study:
- To synthesize and characterize novel heteroleptic iron complexes incorporating a naphthoquinone-type ligand.
- To investigate the structural and magnetic properties of these complexes, focusing on spin-crossover behavior.
- To correlate ligand variations with the observed spin states (high-spin vs. low-spin) in iron(II) complexes.
Main Methods:
- Synthesis of heteroleptic iron complexes with 2-(pyridin-2-yl)-1H-naphtho[2,3-d]imidazole-4,9-dione (HL) and various co-ligands.
- Single-crystal X-ray diffraction for structural characterization at different temperatures (100 K and 270 K).
- Magnetic susceptibility measurements and Mössbauer spectroscopy to probe spin states and SCO behavior.
Main Results:
- Two spin-crossover complexes, [Fe(L)2(ethylenediamine)] and [Fe(L)2(cyclohexanediamine)], exhibited gradual SCO behavior.
- Two homologous iron(II) complexes with diimino benzoquinone and iminosuccinonitrile ligands remained in the low-spin state from 10-300 K.
- An iron(II) complex with water ligands and a tris-chelate complex with protonated HL ligands were found to be high-spin.
Conclusions:
- The naphthoquinone-type ligand (HL) can effectively modulate the spin state of iron(II) complexes.
- Ligand choice is critical in achieving specific spin states and spin-crossover properties in heteroleptic iron complexes.
- These findings contribute to the design of novel iron-based materials with tunable magnetic properties.
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