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Ligand modification transforms a catalase mimic into a water oxidation catalyst.
Wei-Tsung Lee1, Salvador B Muñoz, Diane A Dickie
1Department of Chemistry, Indiana University, 800 East Kirkwood Ave., Bloomington, IN 47405 (USA).
Angewandte Chemie (International Ed. in English)
|July 22, 2014
Summary
Manganese complexes with small N-substituents catalyze hydrogen peroxide disproportionation, while bulky substituents enable water oxidation. This ligand-controlled reactivity switch is key for designing new manganese-based catalysts.
Area of Science:
- Inorganic Chemistry
- Catalysis
- Materials Science
Background:
- High-spin Mn(II) pyridinophane complexes are investigated for catalytic applications.
- The role of N-substituent size in modulating catalytic activity is explored.
Purpose of the Study:
- To report the catalytic reactivity of Mn(II) pyridinophane complexes toward O2 formation.
- To investigate the influence of ligand structure on catalytic pathways for H2O2 disproportionation and H2O oxidation.
Main Methods:
- Synthesis and characterization of high-spin Mn(II) pyridinophane complexes with varying N-substituents (R=H, Me, tBu).
- Evaluation of catalytic activity in aqueous solution for H2O2 disproportionation and electrocatalytic H2O oxidation.
- Control experiments and preliminary mechanistic studies to determine catalyst nature (homogeneous, mononuclear).
Main Results:
- Complexes with small N-substituents (R=H, Me) efficiently catalyze H2O2 disproportionation in water.
- The complex with a bulky N-substituent (R=tBu) shows suppressed H2O2 disproportionation but becomes active for electrocatalytic H2O oxidation.
- Control experiments support a homogeneous, mononuclear catalytic mechanism.
Conclusions:
- Ligand design in Mn(II) pyridinophane complexes enables a switchable catalytic response between H2O2 disproportionation and H2O oxidation.
- This finding has significant implications for the rational design of advanced manganese-based water oxidation catalysts.
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