Molecular Photoelectrocatalyts for Solar Fuel Production: Discovery, Mechanism, and Exploration Public Deposited

Downloadable Content

Download PDF
Last Modified
  • March 20, 2019
  • Pitman, Catherine
    • Affiliation: College of Arts and Sciences, Department of Chemistry
  • An exploration of the chemistry of molecular photoelectrocatalysts, beginning with the Cp*Ir(bpy) framework, is presented. Chapter 1 covers approaches to hydrogen evolution with an eye towards solar fuel production. The importance of both metal-hydride species and methods to measure metal-hydride bond strength is discussed. In Chapter 2, the central complex of this dissertation, [Cp*Ir(bpy)(H)]+, is introduced when in situ electrochemical generation permits the construction of a photoelectrocatalytic cycle. Irradiation of neutral aqueous solutions containing [Cp*Ir(bpy)(H)]+ poised at cathodic potentials produces H2 in high Faradaic efficiency. Chapter 3 presents a general synthetic scheme whereby precipitation of Cp*Ir(bpy) and analogues from water and subsequent reaction with electrophiles enabled access to a wide range of water-soluble metal-hydride and metal-alkyl complexes. Chapter 4 explores the hydricity—the hydride donor ability—of Cp*Ir(bpy)- and (arene)Ru(bpy)-based hydrides. The hydricity of [Cp*Ir(bpy-COO)(H)]– is measured using a potential-pKa cycle, and the hydricities of the metal-hydrides accessed in Chapter 3 are measured relative to this reference complex. The thermodynamic measurements presented explain why [Cp*Ir(bpy)(H)]+ is stable in neutral, aqueous solutions in the dark. Chapters 5 and 6 present results of alterations to the [Cp*Ir(bpy)(H)]+ structure. In Chapter 5, Rh is exchanged for Ir, resulting in an entirely unexpected activation of Cp*. Formation of the transient [Cp*Rh(bpy)(H)][Cl] complex leads to in the more stable species (Cp*H)Rh(bpy)(Cl). The implications of this structure on the reduction of NAD+ are discussed. In Chapter 5, the hydride ligand is exchanged for a methyl ligand making [Cp*Ir(bpy)(CH3)]+. This metal-methyl complex is characterized and its photochemical reactions are explored. Kinetic order, radical traps and clocks, and isotope labelling suggest that excitation results in homolysis of the Ir–CH3 bond.
Date of publication
Resource type
Rights statement
  • In Copyright
  • Brookhart, Maurice
  • Waters, Marcey
  • Gagne, Michel
  • Templeton, Joseph
  • Miller, Alexander
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017

This work has no parents.