Geometry-Driven Field-Induced Single-Ion Magnetism in Hexagonal Bipyramidal Tb³⁺ and Ho³⁺ Complexes

Area of Science:

• Coordination Chemistry
• Magnetochemistry
• Materials Science

Background:

• Single-ion magnets (SIMs) are crucial for developing advanced magnetic materials.
• Lanthanide complexes offer potential for SIM applications due to their unique electronic properties.
• Exploring novel coordination geometries and ligand designs is key to enhancing SIM performance.

Purpose of the Study:

• To synthesize and characterize novel terbium (Tb³⁺) and holmium (Ho³⁺) complexes.
• To investigate the magnetic properties, specifically single-ion magnet behavior, of these new complexes.
• To elucidate the structural and electronic factors governing the observed magnetic phenomena.

Main Methods:

• Synthesis of lanthanide precursors followed by ligand exchange reactions.
• Single-crystal X-ray diffraction for structural determination.
• Magnetic characterization including variable-temperature magnetic susceptibility measurements.
• Ab initio calculations to analyze electronic structure and magnetic interactions.

Main Results:

• Successful synthesis and isolation of Tb³⁺ and Ho³⁺ complexes with triphenylsilanolate ligands.
• X-ray diffraction confirmed a hexagonal bipyramidal coordination geometry for both complexes.
• Complexes exhibit single-ion magnet behavior at an applied field of 2000 Oe.
• These are the first reported Tb³⁺ and Ho³⁺ complexes with this geometry and macrocyclic ligand to show SIM behavior.
• Magnetic relaxation is governed by Raman processes at higher temperatures, with partial suppression of quantum tunneling of magnetization (QTM).

Conclusions:

• The synthesized Tb³⁺ and Ho³⁺ complexes are the first SIMs with a hexagonal bipyramidal geometry and a macrocyclic ligand in a nonsandwich topology.
• Ab initio calculations support experimental findings, explaining the origin of the magnetic behavior through f-orbital energy level splitting.
• These findings advance the design principles for lanthanide-based single-ion magnets.