Bioinspired manganese(II) complexes with a clickable ligand for immobilisation on a solid support

Area of Science:

• Coordination Chemistry
• Bioinorganic Chemistry
• Materials Science

Background:

• The manganese-dependent dioxygenase (MndD) enzyme's active site features a 2-His-1-carboxylate facial chelation motif.
• Mimicking this active site is crucial for developing synthetic analogues with potential catalytic activity.
• Click chemistry offers a robust method for immobilizing metal complexes onto solid supports.

Purpose of the Study:

• To synthesize novel manganese(II) complexes with ligands designed to mimic the MndD active site.
• To explore the grafting of these complexes onto solid supports using click chemistry.
• To investigate the structural, magnetic, and solution properties of the resulting dinuclear and mononuclear manganese complexes.

Main Methods:

• Synthesis of clickable ligands N,N -bis((pyridin-2-yl)methyl)prop-2-yn-1-amine (L(1)) and N-((1-methyl-1H-imidazol-2-yl)methyl)-N-(pyridin-2-ylmethyl)prop-2-yn-1-amine (L(2)).
• Formation of dinuclear manganese(II) complexes with halide or pseudohalide bridges ([Mn2(μ-X)2X2L2]).
• Grafting of complexes onto azido-functionalised MCM-41 silica using click chemistry.
• Characterization using X-ray crystallography, magnetic susceptibility measurements, and electron paramagnetic resonance (EPR) spectroscopy.

Main Results:

• Dinuclear manganese(II) complexes with chloride, bromide, or azide bridges were successfully synthesized and characterized.
• Weak magnetic exchange interactions were observed between the high-spin Mn(II) ions in the dinuclear complexes.
• A magneto-structural correlation for bis(μ1,1-azido)dimanganese(II) complexes was proposed based on structural parameters.
• Solution studies indicated the presence of both dimeric and monomeric species, with grafting stabilizing these forms on MCM-41.

Conclusions:

• The synthesized clickable ligands effectively mimic the MndD active site and allow for facile immobilization.
• The dinuclear manganese(II) complexes exhibit tunable magnetic properties influenced by bridging ligands.
• Grafting onto mesoporous silica provides a stable platform for these manganese complexes, preserving both dimeric and monomeric states.