Slow magnetic relaxation in a trigonal-planar mononuclear Fe(II) complex

Area of Science:

• Coordination Chemistry
• Magnetochemistry
• Materials Science

Background:

• Iron complexes are crucial in various fields, but understanding their magnetic properties, especially single-ion magnet (SIM) behavior, is key for advanced applications.
• Developing new molecular magnetic materials requires precise control over the coordination environment and electronic structure of metal ions.

Purpose of the Study:

• To synthesize and structurally characterize novel iron(III) and iron(II) complexes using a β-diketiminate ligand.
• To investigate the magnetic properties of the synthesized complexes, focusing on single-ion magnet (SIM) behavior.
• To explore the relationship between structural features, electronic configuration, and magnetic anisotropy in iron complexes.

Main Methods:

• Synthesis and structural characterization of iron(III) tetrahedral high-spin complex [LFe^III(Cl)₂] (1) and iron(II) high-spin triangular planar complex [LFe^IICl] (2).
• Reduction of complex 1 to complex 2, observing changes in magnetic anisotropy.
• Experimental magnetic measurements combined with *ab initio* calculations to determine magnetic properties and energy barriers.

Main Results:

• Successful synthesis and structural elucidation of two novel iron complexes.
• Iron(II) complex 2 exhibits field-induced single-ion magnet (SIM) behavior with a significant energy barrier (U_eff = 40.02 K).
• Observation of butterfly hysteresis loops in complex 2 up to 8 K, a first for iron(II) complexes, attributed to intrinsic magnetic anisotropy from spin-orbit coupling.

Conclusions:

• The synthesized iron(II) triangular planar complex demonstrates promising single-ion magnet characteristics.
• The study highlights the importance of ligand design and coordination geometry in achieving desired magnetic properties in iron complexes.
• This work opens new avenues for developing molecular magnets based on earth-abundant iron.