Slow magnetic relaxation in Fe(II) m-terphenyl complexes

Area of Science:

• Coordination Chemistry
• Magnetism
• Materials Science

Background:

• Two-coordinate transition metal complexes offer highly axial coordination environments, ideal for single-molecule magnets (SMMs).
• These complexes exhibit significant magnetic anisotropy, a key property for SMMs.

Purpose of the Study:

• To investigate the magnetic properties of a series of two-coordinate iron(II) m-terphenyl complexes.
• To explore how functionalization of the para-substituent influences the magnetic behavior and relaxation rates of these complexes.

Main Methods:

• Synthesis of five structurally related two-coordinate Fe(II) m-terphenyl complexes with varying para-substituents (R).
• Magnetic characterization to determine field-induced single-molecule magnet behavior.
• Analysis of magnetic relaxation rates using direct and Raman mechanisms.
• Ab initio calculations to predict crystal field and zero-field splitting parameters.

Main Results:

• All five synthesized complexes exhibit field-induced single-molecule magnet behavior.
• Magnetic relaxation rates were successfully modeled by direct and Raman mechanisms.
• Electron-donating para-substituents were found to significantly slow the magnetic relaxation rate.
• Calculations predicted large crystal field splitting (>850 cm-1) and sizable zero-field splitting parameters (ca. -60 cm-1).

Conclusions:

• The study demonstrates that modifying the para-substituent on m-terphenyl ligands can tune the magnetic function of two-coordinate iron complexes.
• m-terphenyl ligands show promise as versatile building blocks for creating effective single-molecule magnets due to their ability to induce highly axial crystal fields.