Model Dimeric Manganese(IV) Complexes Featuring Terminal Tris-hydroxotetraazaadamantane and Various Bridging Ligands

Area of Science:

• Inorganic Chemistry
• Materials Science
• Computational Chemistry

Background:

• Dinuclear manganese complexes are crucial in catalysis and bioinorganic chemistry.
• Understanding the electronic and magnetic properties of manganese complexes is key to designing new functional materials.

Purpose of the Study:

• To synthesize and characterize novel dinuclear manganese(IV) complexes with tetraazaadamantane ligands.
• To investigate the magnetic properties, including antiferromagnetic coupling and zero-field splitting (ZFS).
• To employ computational methods to understand electronic structures and validate experimental findings.

Main Methods:

• Synthesis of dinuclear manganese(IV) complexes with azide, methoxide, and oxalate bridging ligands.
• High-field Electron Paramagnetic Resonance (HF EPR) spectroscopy for magnetic studies.
• Infrared (IR), UV-vis spectroscopy, and cyclic voltammetry for physicochemical characterization.
• Broken-symmetry (BS) and coupled-perturbed (CP) density functional theory (DFT) for theoretical calculations.

Main Results:

• Successful synthesis of three dinuclear manganese(IV) complexes (1-3) featuring tetraazaadamantane ligands.
• Experimental data revealed weak antiferromagnetic coupling and modest zero-field splitting (ZFS) in the complexes.
• Computational studies, particularly CP DFT with B3LYP, accurately reproduced experimental ZFS parameters.
• Evidence suggests manganese sites with increased +3 character supported by redox-noninnocent ligands.

Conclusions:

• The synthesized manganese(IV) complexes exhibit interesting magnetic and electronic properties.
• Computational methods are effective in predicting the ZFS of such systems.
• The tetraazaadamantane ligand plays a crucial role in the electronic structure and redox behavior of the complexes.