Solvent modified spin crossover in an iron(iii) complex: phase changes and an exceptionally wide hysteresis
Wasinee Phonsri1, Phimphaka Harding1, Lujia Liu2
1Functional Materials and Nanotechnology Centre of Excellence (FuNTech) , Walailak University , Thasala , Nakhon Si Thammarat 80160 , Thailand .
Chemical Science
|May 30, 2017
Summary
Solvent choice significantly impacts iron(III) spin crossover (SCO) complex behavior. Even minor structural changes due to solvents dramatically alter SCO characteristics, influencing material properties.
Area of Science:
- Coordination Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Spin crossover (SCO) complexes of iron(III) exhibit distinct high-spin (HS) and low-spin (LS) states.
- The transition between these spin states is sensitive to external stimuli, including solvent molecules.
- Understanding solvent effects is crucial for tuning SCO properties for applications.
Purpose of the Study:
- To investigate the influence of various solvents on the spin crossover behavior of [Fe(qsal-I)2]OTf complexes.
- To correlate structural changes induced by solvent molecules with SCO characteristics.
- To explore the formation of new phases and their impact on spin transitions.
Main Methods:
- Synthesis and characterization of six iron(III) SCO complexes with different solvent molecules (MeOH, EtOH, n-PrOH, i-PrOH, acetone, MeCN).
- Variable temperature magnetic susceptibility measurements to determine SCO transition temperatures and hysteresis.
- Variable temperature powder X-ray diffraction (VT-PXRD) to identify structural phases and their transitions.
Main Results:
- SCO behavior varied significantly with solvent: abrupt in MeOH and EtOH complexes, gradual in propanol complexes, and incomplete in acetone and MeCN complexes.
- Aged ethanol complex ([Fe(qsal-I)2]OTf·EtOH) showed exceptionally wide hysteresis (80 K), while fresh samples exhibited stepped SCO with varying hysteresis (2–42 K).
- VT-PXRD revealed new phases (2b and 2c) in the ethanol complex, with phase 2c undergoing a spin transition at 180 K and phase 2b showing two-step SCO.
Conclusions:
- Solvent molecules play a critical role in dictating the SCO characteristics of [Fe(qsal-I)2]OTf complexes.
- Even subtle structural modifications induced by solvents can lead to dramatic changes in SCO behavior, including transition temperatures and hysteresis.
- The formation of distinct crystalline phases influenced by solvent molecules can lead to complex, multi-step spin transitions.
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