Calculations of pH-Dependent Redox Potentials for Proton-Coupled Electron Transfer Reactions

Abstract

We will present a computational protocol that combines density functional theory (DFT) and cheminformatics approaches to predict redox potentials of organic molecules as a function of the pH of the aqueous solution.[1] The methodology is based on an improved version of the Alberty-Legendre transform to account for varying protonation states of the redox reaction products at different pH values. Our approach circumvents the known problems with the use of DFT calculations and implicit solvation models for highly charged anions. To validate the protocol, we use a consistent set of quinones which can undergo up to two-electron two-proton redox reaction. As the reference we use the experimental redox potentials measured at pH 0, 7, and 13.[2] We demonstrate that with the proposed methodology we can achieve the MAE=0.144 V and MSE=-0.016 V at pH=13.[1] Fornari, R.P.; de Silva, P. A Computational Protocol Combining DFT and Cheminformatics for Prediction of pH-Dependent Redox Potentials. Molecules 2021, 26, 3978.[2] Wedege, K.; Dražević, E.; Konya, D.; Bentien, A. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility. Sci. Rep. 2016, 6, 39101.