Ultrafast Chemical Dynamics of Catalysts and Photoswitches

Abstract

Catalytic or biological mechanisms can be impacted by a change to the catalytic system or its surroundings. To determine and optimize these mechanisms, these effects that occur on an ultrafast timescale must be identified. Experimental techniques that operate on a similar molecular timescale are necessary to capture the evolution of these species over time. We seek to understand how changes in the electronic structure of catalysts and photoswitches impact solvation and structural dynamics. Using ultrafast two-dimensional infrared (2D- IR) spectroscopy, we analyze how changes in the electron density of the Lehn CO2 reduction catalyst Re(bpy)(CO)3Cl affect its vibrational dynamics, finding little to no impact on the solvation dynamics but a significant shift in the carbonyl stretching frequencies. Implementation of a novel 2D-IR spectroelectrochemical experimental design allows us to study the intermediates generated in the electrocatalytic reduction of Re(bpy)(CO)3Cl in situ, allowing us to record the impact of reduction of this molecule on the solvation dynamics. Ultrafast transient polarized X-ray absorption measurements performed on methylcobalamin give a window into structural changes that occur following photoexcitation. Our studies span a variety of ultrafast spectroscopic techniques to gain insight into key intermediate species in electrocatalytic or biological mechanisms.