Issue 20, 2025

Systematic improvement of redox potential calculation of Fe(iii)/Fe(ii) complexes using a three-layer micro-solvation model

Abstract

Electrochemical transformations of metal ions in aqueous media are challenging to model accurately due to the dynamic solvation structure surrounding ions at different charge states. Predictive modeling at the atomistic scale is essential for understanding these solvation architectures but is often computationally prohibitive. In this contribution, we present a simple, fast, and accurate three-layer micro-solvation model to evaluate the redox potential of metal ions in aqueous solutions. Our model, developed and validated for Fe3+/Fe2+ redox potentials, combines the DFT-based geometry optimizations of the octahedral Fe complex with two layers of explicit water molecules to capture solute–solvent interactions and an implicit solvation model to account for bulk solvent effects. This approach yields accurate predictions for Fe3+/Fe2+ redox potentials in water, achieving errors of 0.02 V with ωB97X-V, 0.01 V with ωB97X-D3, 0.04 V with ωB97M-V, and 0.02 V with B3LYP-D3 functionals. We further demonstrate the generality of our model by applying it to additional metal complexes, including the challenging Fe(CN)63−/4− system, where our model successfully achieves close agreement with experimental values, with an error of 0.07 V and an average error of 0.21 V for all five systems. In summary, the presented simple solvation model has broad applicability and potential for enhancing computational efficiency in redox potential predictions across various chemical and industrial processes of metal ions.

Graphical abstract: Systematic improvement of redox potential calculation of Fe(iii)/Fe(ii) complexes using a three-layer micro-solvation model

Supplementary files

Article information

Article type
Paper
Submitted
04 Feb 2025
Accepted
28 Apr 2025
First published
29 Apr 2025
This article is Open Access
Creative Commons BY-NC license

Phys. Chem. Chem. Phys., 2025,27, 10717-10729

Systematic improvement of redox potential calculation of Fe(III)/Fe(II) complexes using a three-layer micro-solvation model

H. Harb and R. Surendran Assary, Phys. Chem. Chem. Phys., 2025, 27, 10717 DOI: 10.1039/D5CP00454C

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