DFT as a Powerful Predictive Tool in Photoredox Catalysis: Redox Potentials and Mechanistic Analysis

Visible-light
photoredox catalysis has come forth as a powerful
activation mode in chemical synthesis, affording the development of
a multitude of new strategies for molecular construction. However,
detailed mechanistic knowledge of the various subprocesses involved
is lacking, and new tools for addressing this are needed to drive
innovation forward in the area. Herein, we describe predictions of
ground- and excited-state redox potentials of ruthenium and iridium
photocatalysts using nonrelativistic and scalar relativistic zero-order
regular approximation density functional theory (DFT) methods. The
computed redox potentials were correlated with experimental values
and found to reproduce them well. Relativistic corrections were found
to be important to reproduce experimental data. Moreover, the computational
protocol allows us to estimate redox potentials that are not currently
available in the literature or are difficult to determine experimentally.
The mechanistic details of the photocatalyzed C–H functionalization
of 1-methylindole with diethyl bromomalonate were also studied using
the validated DFT method. We demonstrate how DFT can predict the experimentally
observed redox behavior of common photocatalysts and mechanistic details
of the C–H functionalization process. This work demonstrates
that DFT can be a powerful tool for innovation and design in the field
of visible-light photoredox catalysis by predicting redox properties
and mechanistic behavior.