Slow magnetic relaxation in a high-spin pentacoordinate Fe(iii) complex

Area of Science:

• Inorganic Chemistry
• Materials Science
• Magnetochemistry

Background:

• Single-molecule magnets (SMMs) are crucial for developing advanced magnetic materials.
• Understanding magnetic relaxation dynamics in coordination complexes is key to designing efficient SMMs.
• Pentacoordinate iron(III) complexes offer unique electronic structures for magnetic studies.

Purpose of the Study:

• To investigate the magnetic relaxation behavior of a mononuclear pentacoordinate iron(III) complex.
• To elucidate the dominant relaxation mechanisms influencing the magnetic properties.
• To correlate relaxation dynamics with the complex's structure and electronic configuration.

Main Methods:

• Synthesis and characterization of the mononuclear pentacoordinate iron(III) complex.
• Variable-temperature magnetic susceptibility measurements.
• High-frequency electron paramagnetic resonance (HFEPR) spectroscopy to probe relaxation dynamics.

Main Results:

• The complex exhibits slow magnetic relaxation, characteristic of a potential single-molecule magnet.
• Three distinct relaxation channels were identified: direct, Raman, and a low-frequency process.
• High-frequency relaxation times (microseconds) increased with decreasing temperature, following direct and Raman processes.
• Low-frequency relaxation times (0.52-0.79 s) showed minimal temperature dependence.

Conclusions:

• The mononuclear pentacoordinate iron(III) complex demonstrates complex magnetic relaxation behavior.
• The observed relaxation dynamics are well-described by a combination of direct, Raman, and low-frequency processes.
• This study provides insights into the design principles for iron-based molecular magnetic materials.