Ultrafast Spectroscopy of Proton-Coupled Electron Transfer (PCET) in Photocatalysis

The main goal of this project is to understand the mechanisms of proton-coupled electron transfer reactions, with particular emphasis on their relevance and utility for solar-to-fuel light harvesting. The main focus of our work has been identifying coupling between the electronic and protonic degrees of freedom in a wide range of materials. In particular, we have sought to identify themes and principles that dictate how protons move in the aftermath of an electronic excitation. The results can be divided into three groups. First, we have studied a molecule with excited state proton transfer capability and two identical protons for transfer. We have correlated the electronic charge density redistribution to proton transferand have identified that electronic relaxation after a single proton transfer extinguishes the propensity of the second proton to transfer. Our work on this system led us to the interesting concept of photobasicity, where light excitation of a photobase can be used to remove a proton from a target molecule. This phenomenon has the potential to be used in photocatalysis.