Linear Correlation Models for the Redox Potential of Organic Molecules in Aqueous Solutions

Abstract

<p>In this study we use the molecular orbital energy approximation (MOEA) and the energy difference approximation (EDA) to build linear correlation models for the redox potentials of 53 organic compounds in aqueous solutions. The molecules evaluated include nitroxides, phenols and amines. Both the MOEA and EDA methods yield similar correlation models, however the MOEA method is less computationally expensive. Correlation coefficients (R2) below 0.3 and mean absolute errors above 0.25 V were found for correlation models built without solvent effects. When explicit water molecules and a continuum solvent model are added to the calculations, correlation coefficients close to 0.8 are reached and mean absolute errors below 0.18 V are obtained. The incorporation of solvent effects is necessary for good correlation models, particularly for redox processes of charged molecules in aqueous solutions. A comparison of the correlation models from different methodologies is provided.<br></p>

Multi-objective goal-directed optimization of de novo stable organic radicals for aqueous redox flow batteries

“…2 (refs. 49,50 ). We obtain an MAE of 0.25 V for 46 molecules using M06-2X/def2-TZVP with SMD solvation, with M06-2X similarly yielding the lowest error among the functionals considered.…”

Experimental Validation of a Computational Screening Approach to Predict Redox Potentials for a Diverse Variety of Redox-Active Organic Molecules

“…Using computational methods to predict the reduction and/or oxidation potentials of redox-active molecules is not a new approach. Early models correlated observed redox potentials against Hammett parameters. , More recently, empirical relationships between experimental redox potentials and HOMO–LUMO gap energies have been established. , However, for fully ab initio predictions of redox potentials, it is necessary to compute the free energy difference between the oxidized and reduced forms of the molecule, as well as the corresponding quantities for a specified reference systemtypically the standard hydrogen electrode (SHE). − …”

“…22,23 More recently, empirical relationships between experimental redox potentials and HOMO−LUMO gap energies have been established. 24,25 However, for fully ab initio predictions of redox potentials, it is necessary to compute the free energy difference between the oxidized and reduced forms of the molecule, as well as the corresponding quantities for a specified reference system typically the standard hydrogen electrode (SHE). 26−29 Using this approach, large-scale computational screening studies have been carried out to identify promising RFB species, 27−29 but these lack experimental validation.…”