In this project supported by the Experimental Physical Chemistry Program, Professor Charles B. Harris of the University of California, Berkeley and his research group will develop novel two-dimensional infrared (2D IR) techniques for the study of transition states in solution. The reactions for study include ligand fluxionality, photoinduced ligand dissociation, and intramolecular electron transfer in mixed-valence complexes. The compounds under study are model systems with well characterized structures and chemistry, but whose molecular dynamics are not well known. The experiments in this project involve the development of new spectroscopic tools that can reveal unprecedented information that will have a fundamental impact on our understanding of chemical reaction dynamics in solution.
Additionally, this research will benefit from a multi-faceted approach involving not only experimental molecular spectroscopy but also synthesis and theory. Students (both graduate and undergraduate) as well as postdoctoral scholars will benefit from this multi-disciplinary research environment. Finally, the Harris group is engaged in a variety of community outreach activities that promote a broader public understanding and appreciation for chemistry and science in general.
Many of our activities on this grant’s projects were focused on expanding the capacity of two- dimensional infrared spectroscopy for understanding ultrafast chemical and physical dynamics in solutions. In terms of the chemical systems and processes studied during this funding period, our focus was primarily centered on understanding ground state ligand exchange mechanisms in organometallic complexes as well as ground state electron transfer processes. The electron transfer projects yielded particularly interesting results, motivating a reinterpretation of a substantial body of existing work surrounding the use of infrared line shapes to predict electron transfer rates from linear infrared spectra. These electron transfer results clearly demonstrated the power and utility of two-dimensional infrared spectroscopy for measuring intramolecular electron transfer rates. In addition to the two-dimensional infrared studies, we also carried out a substantial number of ultraviolet/visible pump–infrared probe experiments, in the spirit of understanding primary events in photochemically initiated organometallic photochemistry. The results of these UV/Vis pump-IR probe experiments explored a variety of topics including solvation dynamics, spin state changes, the photochemistry of transition metal clusters, photochemically initiated electron transfer reactions, and photochemical isomerization mechanisms. Taken as a whole, the results of these studies provide insight into the fundamental steps of organometallic reaction dynamics and are relevant to the broad array of reactions catalyzed by organometallic complexes.
