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Halogen-Driven Spin Dynamics: Exploring Correlation of Cooperativity and Spin Crossover in Solid-State Mononuclear
Li-Wen Chen1, Hai Zhu1, Hua-Wei Zhou1
1State Key Laboratory of Flexible Electronics (LoFE) & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
We synthesized four new iron(III) complexes with halogen-substituted ligands. Complex 2 shows a unique two-step spin crossover, demonstrating how halogens influence magnetic properties in spin crossover (SCO) materials.
Area of Science:
- Coordination Chemistry
- Materials Science
- Magnetism
Background:
- Spin crossover (SCO) materials are of interest for molecular switches and sensors.
- Tuning SCO properties requires understanding ligand effects on metal centers.
- Iron(III) complexes offer a platform for studying spin state transitions.
Purpose of the Study:
- Synthesize and characterize novel mononuclear iron(III) complexes.
- Investigate the influence of halogen substituents on SCO behavior.
- Elucidate the relationship between crystal structure and magnetic properties.
Main Methods:
- Synthesis of four [Fe(5-X-sal2trien)]ReO4 complexes (X = F, Cl, Br, I).
- Magnetic susceptibility measurements to determine spin states and transitions.
- Single-crystal X-ray diffraction at variable temperatures to analyze structural changes.
Main Results:
- Complex 1 (X=F) remains high-spin.
- Complexes 3 (X=Br) and 4 (X=I) show gradual spin crossover above 300 K.
- Complex 2 (X=Cl) exhibits a two-step spin crossover at 250 K and 209 K with structural phase transitions (Pccn-Pmmn-P21/m).
Conclusions:
- Halogen substituents significantly impact the cooperativity and magnetic properties of iron(III) SCO complexes.
- The observed two-step SCO in complex 2 is linked to distinct structural phase transitions.
- This study provides insights into designing SCO materials with tailored properties.
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