Calculation of One-Electron Redox Potentials Revisited. Is It Possible to Calculate Accurate Potentials with Density Functional Methods?

Abstract

Density Functional calculations have been performed to calculate the one-electron oxidation potential for ferrocene and the redox couples for a series of small transition metal compounds of the first-, second-, and third-row elements. The solvation effects are incorporated via a self-consistent reaction field (SCRF), using the polarized continuum model (PCM). From our study of seven different density functionals combined with three different basis sets for ferrocene, we find that no density functional method can reproduce the redox trends from experiment when referencing our results to the experimental absolute standard hydrogen electrode (SHE) potential. In addition, including additional necessary assumptions such as solvation effects does not lead to any conclusion regarding the appropriate functional. However, we propose that if one references their transition metal compounds results to the calculated absolute half-cell potential of ferrocene, they can circumvent the additional assumptions necessary to predict a redox couple. Upon employing this method on several organometallic and inorganic complexes, we obtained very good correlation between calculated and experimental values (R(2) = 0.97), making it possible to predict trends with a high level of confidence. The hybrid functional B3LYP systematically underestimates the redox potential; however, the linear correlation between DFT and experiment is good (R(2) = 0.96) when including a baseline shift. This protocol is a powerful tool that allows theoretical chemists to predict the redox potential in solution of several transition metal complexes a priori and aids in the rational design of redox-active catalysts.

Computational study of the activated O H state in the catalytic mechanism of cytochrome c oxidase

“…Even though such density functional theory (DFT) calculations are challenging (41,42) (Fig. S1, see also Table S2) in such a way that the formal structure should (Fig.…”

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

“…It is worth to be cautious in choosing appropriate DFT functionals for redox potential predictions. Although the B3LYP hybrid (Hartree-Fock-DFT) functional has been found to accurately predict redox potentials for organic compounds, for transition metal complexes, the GGA DFT functional BP86 performed better than the B3LYP one [55][56][57]. Despite these results for transition metals [34], the B3LYP functional has reproduced redox potentials for actinyl complexes in agreement with experimental values in solution.…”

“…The hybrid DFT B3LYP functional combined with the IEF-PCM (integral equation formalism-polarizable continuum model) solvation model resulted in a good prediction of reduction potentials for a series of TM complexes (including metallozenes, metallozenedichlorides, bipyridyine complexes, carbonyl complexes, and maleonitriledithiolate complexes) in non-aqueous solution such as dichloromethane (DCM), acetonitrile, and dimethylformamide (DMF) only if corrected for an inaccurate reference potential [56]. The redox potentials were predicted with a relatively high MUE of 0.54 eV compared to the experimental reduction potentials [56].…”

“…The redox potentials were predicted with a relatively high MUE of 0.54 eV compared to the experimental reduction potentials [56]. The reference used was the calculated Fc/Fc + reference potential.…”

“…In contrast, the GGA BP86 and the PBE functionals performed better than the hybrid DFT functional and the MUE of the predicted reduction potentials was ~0.30 eV smaller than the MUE calculated for the B3LYP predicted reduction potentials. All the predicted B3LYP reduction potentials in this study had to be shifted by a constant value of 0.43 eV to improve the linear correlation between the calculated and the experimental redox potentials [56]. In addition, for a number of iron model complexes of the hydrogenase enzyme, the B3LYP method combined with the PCM solvation model calculated oxidation and reduction potential in CH 3 CN solvent were underestimated and systematic shifts of −0.82 and −0.53 eV had to be added to reproduce the experimental oxidation and reduction potentials, respectively.…”