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Multistep Changes in Spin-Crossover Temperature Induced by Stepwise Desolvations
Taisei Suzuki1, Takuya Shiga1, Natsumi Okawa1
1Degree Programs in Pure and Applied Sciences, Graduate School of Science and Technology, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|July 18, 2026
Summary
This study reveals novel iron(II) spin-crossover (SCO) complex behavior. Stepwise removal of valeronitrile (VN) solvent molecules induces non-monotonic changes in SCO transition temperature and hysteresis.
Area of Science:
- Coordination Chemistry
- Materials Science
- Solid-State Chemistry
Background:
- Lattice solvents critically impact spin-crossover (SCO) properties in metal complexes.
- Multistep SCO transitions driven by solvent removal are infrequently documented.
Purpose of the Study:
- To investigate the effect of stepwise desolvation on the SCO behavior of a novel Fe(II) complex.
- To elucidate the relationship between solvent molecules, intermolecular interactions, and SCO characteristics.
Main Methods:
- Synthesis of a new Fe(II) SCO complex: [Fe(H2L)2](BF4)2·3VN.
- Stepwise desolvation of valeronitrile (VN) solvent molecules.
- Characterization of SCO properties (transition temperature, hysteresis) and structural analysis.
Main Results:
- The complex [Fe(H2L)2](BF4)2·3VN exhibits non-monotonic changes in SCO transition temperature (T1/2) upon sequential VN removal.
- Conversion from 1·3VN to 1·2VN increased T1/2 and hysteresis.
- Further desolvation to 1·VN resulted in partial SCO with decreased T1/2 and enhanced hysteresis.
Conclusions:
- Stepwise desolvation of VN molecules leads to complex, non-monotonic SCO behavior.
- Alterations in intermolecular interactions between VN and the Fe(II) complex are responsible for the observed multistep changes in T1/2.
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