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A Simple Dewar/Cryostat for Thermally Equilibrating Samples at Known Temperatures for Accurate Cryogenic Luminescence Measurements
Published on: July 19, 2016
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Above Room Temperature Spin Transition in Thermally Stable Mononuclear Fe(III) Complexes
Bijoy Dey1, Subhadip Roy1, Ján Titiš2
1Department of Chemistry , IISER Bhopal , Bhopal Bypass Road , Bhauri, Bhopal 462066 , Madhya Pradesh , India.
Inorganic Chemistry
|January 3, 2019
Summary
Two novel iron(III) complexes exhibit high-temperature spin crossover (SCO) behavior, rare for mononuclear systems. Their solvent-free nature and strong intermolecular interactions contribute to exceptional thermal stability above 350 K.
Area of Science:
- Coordination Chemistry
- Materials Science
- Magnetochemistry
Background:
- Spin crossover (SCO) in mononuclear iron(III) complexes is crucial for molecular switches and sensors.
- Achieving high-temperature SCO with high thermal stability remains a significant challenge in coordination chemistry.
- Ligand design plays a critical role in modulating the electronic and structural properties of metal complexes.
Purpose of the Study:
- To synthesize and characterize novel solvent-free mononuclear Fe(III) complexes.
- To investigate the spin crossover behavior and thermal stability of these complexes.
- To explore the influence of ligand conformation on spin transition properties.
Main Methods:
- Synthesis of two mononuclear Fe(III) complexes, [Fe(L)2]NO3 (1) and [Fe(L)2]ClO4 (2), using a π-conjugated azo-phenyl substituted ligand (HL).
- Magnetic susceptibility measurements (2-450 K) to study spin crossover phenomena.
- Thermogravimetric analysis (TGA) to determine thermal stability.
- Differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) for spin crossover characterization.
- Ab initio calculations to analyze electronic energy states.
Main Results:
- Complex 1 exhibits spin crossover above room temperature (T1/2 > 350 K) with a linear ligand conformation.
- Complex 2 shows incomplete spin transition with a skew ligand conformation.
- Both complexes demonstrate exceptional thermal stability up to 496 K due to solvent-free nature and strong intermolecular interactions.
- Ising-like model analysis of complex 1 yielded thermodynamic parameters (ΔH, ΔS, Γ) of the spin transition.
Conclusions:
- The synthesized Fe(III) complexes are rare examples of high-temperature spin crossover materials with remarkable thermal stability.
- Ligand conformation significantly influences the spin crossover behavior in the solid state.
- These findings offer valuable insights for designing advanced molecular materials with tunable magnetic properties.
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