Remaining Unperturbed by the Vibrational Response: Probing Vibrational Coupling, Relaxation, and Solvent Effects with 2D IR Spectroscopy
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Authors
Mallon, Christopher
Issue Date
2025
Type
Dissertation
Language
en_US
Keywords
Cage Correlation Functions , Frequency Fluctuation Correlation Functions , Intramolecular Vibrational Energy Relaxation , Two Dimensional Infrared , Vibrational Coupling , Vibrational Energy Delocalization
Alternative Title
Abstract
Understanding molecular function first requires an understanding of their native structuresand fluctuations of their environments. One of the most powerful ways to probe the dynamic
behavior of molecular systems in solution is through the use of Two-Dimensional Infrared
(2D IR) spectroscopy. 2D IR is an ultrafast laser technique that is capable of probing the
vibrational properties and dynamics down to the picosecond or even femtosecond timescales.
This technique enables the analysis of vibrational couplings, energy redistribution pathways,
and solvation dynamics in real time. The early chapters of this dissertation will provide a semi-rigorous introduction to nonlinearresponse theory and explore newly developed models to more accurately capture the bilinear
coupling strengths between vibrational modes. These support experimental and
computational studies of vibrational energy flow, structural determination, and
solute-solvent interactions. A major focus of the research projects covered in this work will
be on Intramolecular Vibrational Energy Redistribution (IVR) on two key systems. The
first feature aromatic compounds that incorporate a heavy atom (selenium) as a way to block
energy transfer between an azido and cyano vibrational probe. Another involves a
terpyridine-aldehyde ligand that is relevant to spin relaxation in single-molecule magnets. In
both of these works, 2D IR is utilized to reveal vibrational coupling and energy transfer
pathways across the molecular scaffold. The last project that will be discussed is on the detection of localized solvation dynamicsthrough frequency fluctuations correlation functions (FFCFs), where the properties of a
cyanamide vibrational probe placed onto a deoxycytidine nucleoside are investigated in a
variety of viscous environments. This study not only reveals the relationship between the
FFCF decay of the NCN reported and solvent viscosity, but further correlates the decay time
directly with the nanoscale solvent dynamics via molecular dynamics (MD) simulations.