Mn(II) complexes of different nuclearity: synthesis, characterization and catecholase-like activity

Area of Science:

• Coordination Chemistry
• Bioinorganic Chemistry
• Catalysis

Background:

• Compartmental ligands are crucial for designing multinuclear metal complexes.
• Manganese complexes are known for their catalytic activities, including oxidation reactions.

Purpose of the Study:

• To synthesize and structurally characterize novel manganese(II) complexes with "end-off" compartmental ligands.
• To investigate the catecholase-like activity of these complexes and elucidate the underlying catalytic mechanism.

Main Methods:

• Synthesis and structural characterization of manganese complexes.
• Variable temperature magnetic studies to determine magnetic coupling.
• Catecholase activity assays using 3,5-di-tert-butyl catechol (3,5-DTBC).
• Electron Paramagnetic Resonance (EPR) and cyclic voltammetry (CV) studies.

Main Results:

• Three manganese(II) complexes with novel compartmental ligands were synthesized and characterized.
• Complexes displayed significant antiferromagnetic coupling between manganese centers.
• All complexes exhibited high catecholase activity, with a specific activity order observed.
• EPR and CV studies indicated the involvement of ligand-centered radical generation, not metal-centered redox processes.

Conclusions:

• The synthesized manganese complexes are effective catalysts for catechol oxidation.
• The catalytic activity is attributed to a radical pathway involving the ligand, not the manganese metal center.
• This finding provides a new perspective on the mechanism of catecholase-like activity in metal complexes.