Cerium(IV)-driven water oxidation catalyzed by a manganese(V)-nitrido complex

Area of Science:

• Inorganic Chemistry
• Catalysis
• Photochemistry
• Bioinorganic Chemistry

Background:

• Manganese complexes are crucial models for the oxygen-evolving complex in photosystem II.
• Existing manganese-based water-oxidation catalysts (WOCs) typically involve Mn(III) or Mn(IV) oxidation states.
• Current WOCs often exhibit low turnover numbers, particularly with one-electron oxidants like cerium(IV).

Purpose of the Study:

• To investigate manganese(V)-nitrido complexes as a novel class of homogeneous water-oxidation catalysts.
• To evaluate the catalytic activity of a specific manganese(V)-nitrido complex, [Mn(V)(N)(CN)4]2-.
• To explore the potential of the Mn(V)≡N platform for developing advanced WOCs.

Main Methods:

• Synthesis and characterization of manganese(V)-nitrido complexes.
• Homogeneous catalysis experiments using ammonium cerium(IV) nitrate as the terminal oxidant.
• Determination of catalytic performance metrics, including turnover number (TON) and turnover frequency (TOF).

Main Results:

• The manganese(V)-nitrido complex [Mn(V)(N)(CN)4]2- was identified as an active homogeneous WOC.
• The catalyst achieved a turnover number exceeding 180.
• A maximum turnover frequency of 6 min⁻¹ was recorded, indicating significant catalytic efficiency.

Conclusions:

• Manganese(V)-nitrido complexes represent a promising new avenue for designing efficient water-oxidation catalysts.
• The Mn(V)≡N motif can serve as a robust platform for constructing highly active WOCs.
• This study expands the scope of manganese oxidation states applicable to WOC development.