Toward robust electronic coupling predictions in redox-active TEMPO/TEMPO+ systems

Area of Science:

• Materials Science
• Computational Chemistry
• Electrochemistry

Background:

• Organic radical batteries utilize redox-active molecules like TEMPO.
• Understanding electronic coupling is crucial for battery performance.
• Accurate calculation of electronic coupling is computationally challenging.

Purpose of the Study:

• To investigate electronic coupling in TEMPO and TEMPO+ redox pairs.
• To compare various computational methods for calculating electronic coupling.
• To identify the most cost-effective and accurate method for TEMPO systems.

Main Methods:

• Classical molecular dynamics simulations.
• Complete active space self-consistent field (CASSCF) with n-electron valence state perturbation theory (NEVPT2).
• Time-dependent density functional theory (TD-DFT) and DFT-based frontier molecular orbital (FMO) methods.

Main Results:

• Electronic coupling depends exponentially on distance and significantly on orientation.
• Coupling values vary up to 0.2 eV with notable basis set dependency at short distances.
• DFT-based FMO method shows limitations at short intermolecular distances due to orbital mixing.

Conclusions:

• A comprehensive comparison of computational methods for electronic coupling in TEMPO systems was performed.
• The study provides insights into the factors affecting electronic coupling (distance, orientation, basis set).
• Identified the most cost-accurate method for calculating electronic couplings in TEMPO-TEMPO+ systems.