Radical O-O coupling reaction in diferrate-mediated water oxidation studied using multireference wave function theory

Area of Science:

• Catalysis and Reaction Mechanisms
• Computational Chemistry
• Quantum Mechanics

Background:

• Oxygen-oxygen bond formation is crucial for water oxidation catalysis.
• Potassium ferrate (K2FeO4) catalyzes water oxidation via a diferrate intermediate.
• Previous studies suggested an intramolecular oxo-coupling mechanism.

Purpose of the Study:

• To perform a detailed examination of the diferrate-mediated O-O bond formation.
• To investigate the electronic structure and bonding during O-O bond formation.
• To validate the direct oxo coupling mechanism using advanced computational methods.

Main Methods:

• Scalable multireference electronic structure theory.
• Ab initio density matrix renormalization group (DMRG) calculations.
• Complete active space second-order perturbation (CASPT2) and multireference configuration interaction (MRCI) methods.

Main Results:

• High-dimensional correlated many-electron wave functions were computed for the O-O bond formation pathway.
• Large active spaces (36 electrons in 32 orbitals) were utilized to capture complex electronic interactions.
• Calculations confirmed the viability of the direct oxo coupling mechanism and provided potential energy profiles.

Conclusions:

• The direct oxo coupling mechanism in diferrate-mediated water oxidation is computationally validated.
• Advanced multireference methods are essential for accurately describing the electronic structure of multivalent iron-oxo systems.
• The study provides insights into the bonding nature of Fe-O and O-O bonds during catalysis.