Using Steady-state Vibrational Spectroscopy to Characterize the Effect that Molecular Environments have on the Kinetics of Chemical Systems

Open Access
Author:
Giordano, Andrea Nicole
Graduate Program:
Chemistry
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 25, 2014
Committee Members:
  • Benjamin James Lear, Dissertation Advisor
  • Lasse Jensen, Committee Member
  • Tom Mallouk, Committee Member
  • Renee Denise Diehl, Special Member
Keywords:
  • Raman Spectroscopy
  • IR Spectroscopy
  • Molecular environments
  • Kinetics
  • Fe(CO)3(eta^4-norbornadiene)
Abstract:
A goal that unifies all chemists is the desire to understand the intermolecular and intramolecular interactions that occur in a given system. For many chemical systems, we have an understanding of the intramolecular interactions that occur within a molecule, and how these interactions dictate the physical properties of the molecule, such as the dipole moment, color, or the dielectric constant. The intermolecular interactions that occur between molecules and their molecular environment have proven to be more difficult to isolate, due to multiple interactions occurring simultaneously. It is important to understand these interactions between molecules and their molecular environment because such interactions affect nearly every practical chemical system, from biological to industrial applications. Therefore, it is of the upmost importance to understand how the intermolecular interactions can manifest throughout chemical systems. We are interested in separating the multiple contributions to the intermolecular interactions that arise from the molecular environment. To achieve this goal, I developed theoretical and experimental frameworks for determining kinetic parameters of chemical systems using steady-state vibrational spectroscopy, a tool that has proven very powerful for determining the effects of both intramolecular and intermolecular interactions, therefore, we have chosen to focus on using vibrational spectroscopy in my dissertation. I first demonstrate the equivalency between the kinetic information extracted from IR and Raman spectroscopies by obtaining identical activation energies for the ligand site exchange of Fe(CO)3(η4-norbornadiene) (FeNBD). These experiments rely upon the extraction of kinetic information from steady-state band shapes and demonstrated that either vibrational spectroscopic technique can be used to extract kinetic information from the band shapes of steady-state spectra. In order to do this, I worked with collaborators to extend the theoretical framework for extracting the rate constant from the band shapes of vibrational spectra to include Raman spectroscopy. The next step towards the goal of separating the multiple contributions to the intermolecular interactions is to categorize these contributions as static effects and dynamic effects. For the purpose of this work, I define static effects as those that arise from solute-solvent interactions that cause changes in the band shape, while dynamic effects are those that arise from changes in the dynamics of a system as a result of interaction with the molecular environment. I establish a way to separate static effects from dynamic effects by analyzing the solvent effects of Fe(CO)3(η4-cyclooctatetraene) using solvent-dependent IR spectroscopy. The dynamic effects induced by the solvent environment were analyzed through temperature-dependent Raman experiments of FeNBD in a series of linear alkane solvents. The last part of this dissertation further focused on the consequences of static effects, examining the morphology of conducting polymer films used in thin film devices. We used Raman spectroscopy to characterize the crystallinity of conducting polymer films with and without dopant materials. From this data, we constructed structure-function relationships by correlating the morphology of the polymer film to the overall device performance that will aid in the rational design of materials used in thin film devices. This part of my dissertation was done in collaboration with Prof. Elizabeth von Hauff at The University of Freiburg in Germany. Future experiments will explore the effects confining environments will have on the dynamics of FeNBD. Initial experiments to encapsulated FeNBD into a porous polymer matrix were successful, but there are many potential experiments along this line of reasoning that could be explored, and are discussed in the final chapter of this dissertation. In its entirety, this dissertation will provide the scientific community with a novel approach that combines the ability to measure ground state kinetics using steady-state vibrational spectroscopy with a theoretical framework to analyze the effects the molecular environment induces on the ground state kinetics in chemical systems.