Pathway analysis of super-exchange electronic couplings in electron transfer reactions using a multi-configuration...

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Chemical Physics

Background:

• Electron transfer reactions are fundamental in chemistry and biology.
• Accurate calculation of electronic couplings is crucial for understanding electron transfer rates.
• Existing methods often neglect important electronic correlation and orbital relaxation effects.

Purpose of the Study:

• To present a novel pathway analysis of super-exchange electronic couplings in electron transfer reactions.
• To develop a method that accounts for non-dynamical electron correlation and orbital relaxation.
• To identify and quantify contributions of individual tunneling pathways.

Main Methods:

• Utilizing localized molecular orbitals from multi-configuration self-consistent field (MCSCF) calculations.
• Employing the occupation restricted multiple active spaces (ORMAS) method to generate configuration state functions (CSFs).
• Applying perturbative methods (Löwdin projection-iteration and higher-order super-exchange) to calculate electronic couplings.

Main Results:

• Electronic couplings calculated via perturbative methods agreed well with non-perturbative results.
• Identified main tunneling pathways involve a few lower-order super-exchange contributions.
• Demonstrated significant contributions of interference among higher-order super-exchange pathways.

Conclusions:

• The developed method accurately captures non-dynamical electron correlation and orbital relaxation effects.
• The analysis provides detailed insights into the nature and contributions of tunneling pathways.
• This approach offers a more comprehensive understanding of electron transfer mechanisms compared to methods ignoring these effects.