Studies of a linear single-molecule magnet.

Area of Science:

• Inorganic Chemistry
• Molecular Magnetism
• Coordination Chemistry

Background:

• Dinuclear manganese complexes are foundational in studying magnetic exchange interactions.
• Understanding spin states and zero-field splitting is crucial for developing single-molecule magnets.
• The ligand cis,cis-1,3,5-cyclohexanetriol (H3cht) offers unique coordination possibilities.

Purpose of the Study:

• To synthesize and characterize a novel trinuclear manganese complex.
• To investigate the magnetic properties, including exchange interactions and spin ground state.
• To explore the potential for slow magnetic relaxation and energy barriers in the complex.

Main Methods:

• Synthesis of the trinuclear complex [Mn3(Hcht)2(bpy)4](ClO4)3 via reaction of [Mn2O2(bpy)4](ClO4)3 with H3cht.
• Dc magnetic susceptibility measurements to determine magnetic exchange and spin states.
• W-Band Electron Paramagnetic Resonance (EPR) spectroscopy to confirm ground state and zero-field splitting (ZFS) parameters.
• Single crystal dc relaxation decay and hysteresis loop measurements to assess magnetic relaxation dynamics.
• Density functional theory (DFT) studies to computationally investigate magnetic coupling.

Main Results:

• The formation of the trinuclear complex [Mn3(Hcht)2(bpy)4](ClO4)3.Et2O.2MeCN was confirmed.
• Weak ferromagnetic exchange coupling between the three Mn ions was observed, leading to a spin ground state of S = 7.
• Zero-field splitting parameters (D and B4(0)) were determined, indicating a breakdown of the strong exchange limit approximation.
• The complex displays an appreciable energy barrier to magnetization relaxation, evidenced by temperature- and sweep rate-dependent hysteresis loops.
• DFT calculations corroborated the ferromagnetic exchange interactions.

Conclusions:

• The synthesized trinuclear manganese complex exhibits promising magnetic properties, including a high spin ground state and evidence of slow magnetic relaxation.
• The observed magnetic behavior is influenced by the interplay between exchange coupling and single-ion zero-field splitting.
• This study contributes to the field of molecular magnetism by demonstrating a new route to high-spin manganese clusters with potential for magnetic memory applications.