Photoredox catalysis has enabled researchers to overcome previously intractable problems in organic synthesis. The use of light to drive catalysis has allowed for more selective reactions that generate both simple and complex molecules from renewable and economical starting materials under mild conditions. The dynamics of these catalysts following photoexcitation determines their efficiency. A direct time-resolved photophysical view of reactions is essential to construct the full kinetic scheme, observe the intermediates, and thereby link dynamics to structure. Through the use of ultrafast broadband transient absorption and two-dimensional electronic spectroscopy across a wide range of time and energy scales, the Huxter group studies photoinduced single-electron transfer and electronic dynamics in photoredox catalytic and radical systems. These studies have revealed complex mechanisms of photoredox catalytic reactions, including the involvement of reduced solvent as intermediates, multiple photoproducts as well as many productive and unproductive pathways. The study of transition metal complexes has also opened new possibilities for versatile reactive pathways. In this talk, we will present our latest research on a novel series of tripyrrindione molecules, which possess tunable redox-active chemistry. Using ultrafast nonlinear spectroscopy, we explore the dynamics of these molecules and how they are influenced by hydrogen-bonding interactions with the solvent, reversible antiferromagnetic coupling and by the oxidation states of the metal centers. The results of these studies will highlight the potential of tripyrrindione molecules for new redox-active chemistry, catalytic applications, and optical sensing.


Vanessa Huxter (University of Arizona)