Elucidating the Role of Transition Metal Electronic Structure in Catalysis and Spin Relaxation

Transition metal complexes are the workhorses of physical inorganic chemistry and have diverse applications in catalysis and quantum information science, especially. The primary descriptor of transition metal complexes, and a good predictor of their utility, is their electronic structure. Notably, rigorous characterization of the spin states, oxidation states, excited states, and magnetic properties of these complexes is necessary to gain mechanistic detail for these applications; this thesis focuses on elucidating the role of transition metal electronic structure in catalysis and spin relaxation. Chapter 1 introduces important transition metal electronic structure considerations and motivates these studies. Part I includes Chapters 2–4 and considers complexes relevant for CO₂ reduction chemistry and cross-coupling reactivity. Chapter 2 investigates the conditions under which a CO₂ reduction catalyst, Fe-p-TMA, undergoes speciation changes and characterizes its excited-state identities and lifetimes. Chapter 3 considers the electrochemical conditions under which highly reduced CO reduction products are generated in an iron porphyrin system, and important connections to photocatalysis are made. Chapter 4 compares the excited-state identities and reactivities of prototypical and tethered Ni(II)–bpy aryl halide complexes. Part 2 includes Chapters 5–6 and focuses on spin relaxation, a key figure of merit in quantum information science. Chapter 5 investigates the effect of structural distortions in S = ½ copper porphyrin systems on their spin-lattice relaxation times, and Chapter 6 moves to identifying the mechanism of spin relaxation in an S = 1 Cr(o-tolyl)₄ system. Together, these compiled studies reveal the nuanced roles of transition metal electronic structure in catalysis and spin relaxation and highlight the importance of their characterization for developing optimized systems.