Density Functional Theory as a Predictive Tool for Cerium Redox Properties in Nonaqueous Solvents

Two methods to correlate
and predict experimental redox potentials for cerium complexes were
evaluated. Seventeen previously reported cerium complexes were computed
using DFT methods in both the CeIII and CeIV oxidation states with a dichloromethane solvent continuum. In the
first computational approach, the ΔGo​(CeIV/​CeIII) was determined for each of the compounds and
these values were correlated with the experimental E1/2 values measured in dichloromethane, referenced to
the ferrocene/​ferrocenium couple. The second method involved
correlating the energies of the CeIV LUMOs (lowest unoccupied
molecular orbitals) with the experimental redox potentials, E1/2. The predictive capabilities of these two
correlative methods were tested using a new cerium hydroxylamine complex,
Ce­(ODi­NOx)2 (ODi­NOx = bis­(2-tert-butyl­hydrox­ylami­nato­benzyl) ether). All
18 complexes studied in this paper were combined with the 15 complexes
determined in acetonitrile from a previously published correlation
by our group. These sets of data allowed us to develop two methods
for predicting the redox potential of cerium complexes regardless
of the solvent for the experimental measurement.