A protocol to evaluate one electron redox potential for iron complexes.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Inorganic chemistry

Background:

• Accurate prediction of spin states and redox potentials is crucial for understanding iron complex behavior.
• Existing computational methods often struggle with the complexities of iron's electronic structure.

Purpose of the Study:

• To develop and validate a robust computational protocol for predicting the ground spin state and redox potentials of iron complexes in acetonitrile.
• To improve the accuracy of density functional theory (DFT) calculations for iron-containing systems.

Main Methods:

• Utilized density functional theory (DFT) with the B3LYP functional and spin-state-corrected basis sets.
• Developed a novel protocol involving structural optimization (B3LYP/6-31G*) and single-point energy calculations with modified basis sets (Fe: s6-31G*, ligands: 6-31+G*).
• Incorporated solvation energy using a polarized continuum model, including cavity creation energy adjusted by natural population analysis (NPA) charge.

Main Results:

• The protocol correctly predicted the ground spin state for 17 out of 18 known iron complexes.
• Achieved a mean absolute error of 0.112 V for open circuit voltage (OCV) calculations.
• Demonstrated a strong correlation between calculated and experimental OCV values.

Conclusions:

• The developed DFT protocol offers high accuracy for determining the ground spin state and redox potentials of iron complexes.
• This computational approach provides a reliable tool for researchers studying iron electrochemistry.
• The method's success in predicting OCV highlights its potential for electrochemical applications.