Fundamental insights into electron transfer reactions of cyclometalated ruthenium donor-bridge-acceptor compounds Public Deposited

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  • Piechota, Eric J.
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • Electron transfer reactions underlie the whole of chemistry: from C-H bond formation, to molecular electronics, and in complex proteins found in nature. Accordingly, much of chemistry relies on developing methods to understand and control such reactions to permit the rational design of molecules toward answering contemporary scientific questions. A common approach is the use of model systems which allow theoretical expectations to be tested experimentally. Chapter 1 establishes the framework on which the dissertation is focused through introducing theoretical expectations and predictions for intra- and interfacial electron transfer reactions through a general mathematical and physically intuitive approach. Additionally, the distinction between non-adiabatic and adiabatic reaction mechanisms is made. This remainder of the Dissertation utilizes model systems of cyclometalated RuII donor-bridge-acceptor compounds to explore mechanisms and pathways through which electron transfer occurs. The donor-bridge-acceptor compounds are covalently linked through a synthetically modifiable aryl-thiophene bridge to an electron-rich triphenylamine unit. Chapter 2 introduces the steady-state spectroscopic, electrochemical, and spectroelectrochemical characterization of the compounds in fluid solution and anchored onto thin films of TiO2. Further, Chapter 2 quantifies the donor-acceptor electronic coupling using UV/Vis/NIR spectroscopy and identifies two pathways through which optical electron transfer can occur, either directly or indirectly. Chapters 3 and 4 highlight the experimental distinction between adiabatic and non-adiabatic electron transfer using temperature dependent kinetics to determine the rate constant and barriers associated with intramolecular electron transfer. In Chapter 3, the kinetic data indicate that the free energy for the reaction is reduced when the electronic coupling is large. Chapter 4 quantifies the free energies of activation demonstrating that the free energy of activation was independent of reaction (non)adiabaticity. Chapters 5 and 6 investigates interfacial electron transfer from either a TiO2 surface or a core/shell SnO2/TiO2 to a molecular acceptor, either the Ru center or triphenylamine unit. Electron transfer from the interface to the triphenylamine unit was found to be bridge independent and indicates that discrete sets of orbitals constitute an electron transfer pathway discussed in Chapter 5. Chapter 6 compares activation energies for interfacial electron transfer on SnO2/TiO2 toward determination of electron transfer occurs as an activated or tunneling process.
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Advisor
  • Atkin, Joanna M
  • Dempsey, Jillian L
  • Meyer, Gerald J
  • Cahoon, James F
  • Moran, Andrew
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2019
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