Solvent Effect on the Potential Energy Surfaces for the One-Electron Reduction of CF₃X (X = Cl, Br, I) Molecules: A DFT PCM Study

Abstract

In this article, an effect of solvent on potential energy surfaces, constructed at the PBE1PBE/aug-cc-pVTZ level vs C-X distances for the neutral molecules CF(3)X (X = Cl, Br, I) and the corresponding radical anions CF(3)X¯, is studied using the polarizable continuum model (PCM). The properties and energy changes in these compounds in the presence of argon, acetonitrile (ACN), and dimethyl sulfoxide (DMSO) are compared to the results obtained earlier in vacuo. The presence of solvent very weakly influences the neutral molecules, but it significantly changes properties of radical anions, such as structural parameters and partial charges on atoms. The effect of solvent is manifested also in strong modification of the potential energy surfaces, on which the minima corresponding to the locally stabilized forms of CF(3)X¯ are shallower in argon, and in ACN and DMSO, they almost disappear. This in turn results in much higher energy barriers (by about 0.2-0.3 eV) for the reductive cleavage of C-X bonds in polar solvents than in vacuo. Despite different dielectric constants of ACN and DMSO, the potential energy surfaces obtained in these two solvents are very similar, and the activation energies equal, respectively, 0.635 and 0.637 eV for CF(3)Cl; 0.479 and 0.481 eV for CF(3)Br; and 0.336 and 0.337 eV for CF(3)I.

Modeling of electron transfer across electrochemical interfaces: State‐of‐the art and challenges for quantum and computational chemistry

“…Non‐parabolic potentials describing a strong reorganization of the inner sphere including the chemical bond break can be readily constructed by using the DFT calculations (see some examples for electrochemical reactions in Refs. ). An important point here is to take into account the solvent effects which were addressed by the authors in terms of the Polarized Continuum Model (PCM).…”

“…). An important point here is to take into account the solvent effects which were addressed by the authors in terms of the Polarized Continuum Model (PCM).…”

Simulations of Adiabatic Electrochemical Reduction of the CF3I Molecule—Assessment of Different Models

“…Theoretical investigations of these processes are mostly focused on selected properties of substrates and products in the gas-phase; 1,30−51 the solvent effect. 2,24,52 For the analysis of the reaction mechanism the most important works are those providing potential energy profiles (PES) of the neutral molecules and anions with respect to the C−X bond dissociation. In the article of Bertran et al 24 the PES obtained at the MP2/4-31G* level for the CF 3 Cl and CF 3 Cl¯molecules in the gas phase and in the polar solvent, introduced via the polarizable continuum model (PCM) with dielectric constant ε = 37, were presented.…”

“…The essential step in such reactions is the transfer of an electron from the electrode to the neutral CF 3 X (X = Cl,Br,I) molecules, which in solutions occurs with the simultaneous rupture of the C–X bond and formation of the radical CF 3 and anion X¯. Theoretical investigations of these processes are mostly focused on selected properties of substrates and products in the gas-phase; ,− very few take into account the solvent effect. ,, For the analysis of the reaction mechanism the most important works are those providing potential energy profiles (PES) of the neutral molecules and anions with respect to the C–X bond dissociation. In the article of Bertran et al the PES obtained at the MP2/4-31G* level for the CF 3 Cl and CF 3 Cl¯ molecules in the gas phase and in the polar solvent, introduced via the polarizable continuum model (PCM) with dielectric constant ε = 37, were presented.…”

“…The potential energy surface used in the simulations is based on the Newns–Anderson–Schmickler Hamiltonian and on the analytical potentials fitted to points obtained from quantum calculations for the CF 3 I neutral molecule and anion. Two different sets of points were used for fitting: the first obtained in vacuo and the second in dimethyl sulfoxide, which yields two models, named respectively “VAC” and “SOLV.” Additionally, each model was tested with two different values of the solvent reorganization energies: λ = 0.624 eV and λ = 1 eV. The results show that both models provide results which are qualitatively similar but differ quantitatively, mainly due to a shift in the overpotential η.…”