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Cooperative Iron(II) spin crossover complexes with N4O2 coordination sphere
Birgit Weber1, Eike Kaps, Jan Weigand
1Department of Chemistry and Biochemistry, Ludwig Maximilian University Munich, Butenandtstrasse 5-13 (Haus D), D-81377 München, Germany. bwmch@cup.uni-muenchen.de
Inorganic Chemistry
|December 22, 2007
Summary
Two novel spin crossover complexes exhibit cooperative spin transitions with distinct thermal hysteresis loops. Complex 2 shows potential for photomagnetic applications, demonstrating light-induced excited spin state trapping.
Area of Science:
- Coordination Chemistry
- Materials Science
- Solid-State Physics
Background:
- Spin crossover (SCO) complexes are molecular materials exhibiting a reversible switch between low-spin and high-spin states.
- SCO phenomena are driven by external stimuli like temperature, pressure, or light, making them promising for molecular devices.
- Investigating SCO complexes with cooperative transitions is crucial for understanding and designing advanced functional materials.
Purpose of the Study:
- To synthesize and characterize two new spin crossover complexes, [FeL(py)(2)] (1) and [FeL(DMAP)(2)] (2).
- To investigate their spin transition properties, including cooperativity and thermal hysteresis.
- To explore potential photomagnetic behavior and light-induced effects.
Main Methods:
- Temperature-dependent magnetic susceptibility measurements.
- Thermogravimetric analysis (TGA).
- Mössbauer spectroscopy and X-ray structure analysis.
- Temperature-scanning calorimetry.
- Reflectivity measurements and SQUID magnetometry.
Main Results:
- Both complexes displayed cooperative spin transitions with varying thermal hysteresis widths (2 K for complex 1, 9 K for complex 2).
- X-ray analysis revealed elastic interactions driving cooperativity, more pronounced in complex 2 due to short Fe-Fe distances.
- The spin transition correlated with a change in the O-Fe-O angle.
- Complex 2 exhibited photomagnetic properties, including light-induced excited spin state trapping (LIESST) at 53 K.
Conclusions:
- The synthesized iron(II) complexes exhibit cooperative spin crossover behavior driven by elastic interactions.
- Complex 2 demonstrates significant photomagnetic properties, indicating potential for light-switchable molecular devices.
- The study provides insights into the structure-property relationships governing SCO phenomena.
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