posted on 2023-12-12, 17:37authored byThomas
Dalton Andress, Jackson W. Maxwell, Ashley S. McNeill, David M. Stanbury, David A. Dixon
The aqueous electron affinity and
aqueous reduction potentials
for F•, Cl•, Br•, I•, OH•, SH•, SeH•, TeH•, ClO•, BrO•, and IO• were calculated
using electronic structure methods for explicit cluster models coupled
with a self-consistent reaction field (SMD) to treat the aqueous solvent.
Calculations were conducted using MP2 and correlated molecular orbital
theory up to the CCSD(T)-F12b level for water tetramer clusters and
MP2 for octamer cluster. Inclusion of explicit waters was found to
be important for accurately predicting the redox potentials in a number
of cases. The calculated reduction potentials for X• and ChH• were predicted to within ∼0.1
V of the reported literature values. Fluorine is anomalous due to
abstraction of a hydrogen from one of the surrounding water molecules
to form a hydroxyl radical and hydrogen fluoride, so its redox potential
was calculated using only an implicit model. Larger deviations from
experiment were predicted for ClO• and BrO•. These deviations are due to the free energy of solvation of the
anion being too negative, as found in the pKa calculations, and that for the neutral being too positive
with the current approach.