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Mononuclear Fe(III) complexes with 2,4-dichloro-6-((quinoline-8-ylimino)methyl)phenolate: synthesis, structure, and
Ah Rim Jeong1, Si Ra Park2, Jong Won Shin1
1Department of Chemistry, Kyungpook National University, Daegu 41566, Republic of Korea. jwshin@kisti.re.kr.
Dalton Transactions (Cambridge, England : 2003)
|March 28, 2024
Summary
Three new iron(III) coordination complexes were synthesized and studied. Their spin crossover properties varied significantly between solid and solution states, influenced by counterions.
Area of Science:
- Coordination Chemistry
- Materials Science
- Solid-State Chemistry
Background:
- Iron(III)-based coordination complexes are of interest for their magnetic properties.
- Spin crossover (SCO) phenomena in metal complexes offer potential for molecular switches and sensors.
- Understanding the influence of ligands and counterions on SCO behavior is crucial for designing new materials.
Purpose of the Study:
- To synthesize and characterize novel Fe(III) coordination complexes with a specific ligand.
- To investigate the spin crossover properties of these complexes in both solid and solution states.
- To explore the impact of different counterions (nitrate, tetrafluoroborate, perchlorate) on SCO behavior and relaxation dynamics.
Main Methods:
- Synthesis of three Fe(III) coordination complexes: [Fe(dqmp)2](NO3)·H2O (1), [Fe(dqmp)2](BF4)·2CH3COCH3 (2), and [Fe(dqmp)2](ClO4) (3).
- Structural characterization using single-crystal X-ray crystallography.
- Magnetic property investigations in solid and solution states, including temperature-dependent studies and relaxation time measurements (T1, T2).
Main Results:
- All synthesized complexes exhibited meridional structures with two tridentate dqmp- ligands coordinated to Fe(III).
- Complex 1 showed abrupt, complete spin crossover at 225 K in the solid state, while complexes 2 and 3 displayed incomplete SCO at 135 K and 150 K, respectively.
- In solution, SCO behavior was counterion-dependent; complex 1 showed incomplete SCO, whereas complexes 2 and 3 exhibited more complete transitions than in the solid state. Relaxation times T1 and T2 increased with temperature.
Conclusions:
- The counterion plays a critical role in modulating spin crossover behavior in Fe(III) complexes, particularly in solution.
- Complexes 2 and 3 demonstrate enhanced spin transition completeness in solution compared to the solid state.
- The studied complexes exhibit distinct magnetic relaxation dynamics influenced by temperature and counterion identity.
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