Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
Ricardo B. Metz
The study of the non-covalent interactions between metals ions and ligands such as water and methane are key to understanding many processes including solvation, homogeneous catalysis and metals in biology. Similarly, the study of interactions between transition metal ions and cluster ions with hydrocarbons is of great importance in the understanding of C-H activation reactions which are involved in generation of fuels. Gas-phase metal complexes are good models for understanding the intrinsic interactions between the metal and the ligand. Understanding the mechanisms behind these interactions can be done by characterizing the structure and bonding in the molecular reactants, products, and intermediates. This characterization is made possible by combining experimental spectroscopy with computational studies to provide insight into molecular geometries and binding characteristics of ions. In this work, we explore two non-covalent interactions involved in solvation and catalysis by studying entrance-channel complexes of the reactions of transition metal ions with water and methane respectively.
The motivations, techniques, apparatus, data acquisition and analysis methods are discussed in Chapters 1 and 2. Chapter 3 discusses the electronic spectroscopy of the 7B1 and 7B2 excited states of Mn+(H2O) and Mn+(D2O) measured using photodissociation spectroscopy. Progressions in the Mn+-H2O stretch are observed in both excited states, with the in-plane-bend also observed in the first excited state of Mn+(H2O), and the out-of-plane bend observed in the second excited state of both Mn+(H2O) and Mn+(D2O). Partially resolved rotational structure in the first excited state is analyzed.
Chapter 4 discusses the vibrational spectroscopy of Fex+(CH4)n. Vibrational spectra are measured for Fe2+(CH4)n (n=1-3), Fe3+(CH4)n (n=1-3), and Fe4+(CH4)4 in the C-H stretching region (2650-3100 cm-1) using photofragment spectroscopy, monitoring loss of CH4. All spectra are dominated by an intense peak around 2800 cm-1, due to the symmetric C-H stretch. Density functional theory calculations are used to identify possible structures and geometries and to predict the spectra.
Chapter 5 identifies possible extensions of the Chapter 3 and 4 studies to new first, second, and third-row transition metal-water and metal-methane complexes, as well as complexes of metal cluster ions with water and methane. Lastly, Chapter 5 describes alterations to the instrument.
Copeland, Christopher, "Spectroscopic Studies of Gas-Phase Transition Metal Complexes of Cations and Cluster Ions with Methane and Water" (2017). Doctoral Dissertations. 1058.