Nocera, Daniel G.Campbell, Brandon Michael2026-07-0720262026-06-052026Campbell, Brandon Michael. 2026. Unlocking Super-Oxidizing Electrophotocatalysis via Charge Transfer Excitation of Ag(II) Complexes. Doctoral Dissertation, Harvard University Graduate School of Arts and Sciences.32575063https://dash.harvard.edu/handle/1/42744003At the heart of photochemistry lies the conversion of photonic energy into chemical potential. The manipulation of electron density induced by light absorption provides the impetus for challenging chemical transformations that are oftentimes inaccessible from the thermal ground state. In this way, the photon may be thought of as a reagent with innumerable applications. In many regards, it is the ideal reagent as the photon is clean, selective, traceless, and inexhaustible. However, the efficient utilization of photons toward a given purpose is nontrivial. In recent years, photoredox methodologies have emerged as indispensable tools in organic synthesis as they are able to drive challenging chemical reactions under mild conditions. Central to the success of photoredox is the photocatalyst whose responsibility is two-fold: the capture of a photon and subsequent use of its provided energy. Once a photocatalyst has harvested photonic energy, it may interact with substrates through a variety of mechanisms. Chief among these is single-electron transfer (SET), which generates high-energy, open-shell intermediates that may be harnessed for useful and intuitive bond connections. Photocatalytic production of radical intermediates offers an alternative to thermal, polar pathways of bond construction, which often require harsher conditions. However, photoredox is fundamentally limited by the ability of the photocatalyst to activate substrates through SET. This dissertation is concerned with the design and utilization of “super-oxidizing” (electro)photocatalysts based upon silver in its divalent oxidation state that seek to unlock access to even the most redox-reticent of substrates. In Chapter 1, a brief historical overview of the field of photochemistry is presented, and the basic photophysical principles underlying photoredox catalysis are introduced. For outer-sphere SET, the derivation of excited state redox potential is discussed, and it is shown that classical photocatalysts operate within an ca. ± 2 V vs SCE (saturated calomel electrode) regime. As an alternative strategy, ligand-to-metal charge transfer (LMCT) can furnish radicals from redox-reticent substrates with oxidation potentials beyond 2 V vs SCE through intramolecular SET. The design principles for LMCT photocatalysts are outlined from a molecular orbital (MO) theory perspective, and it is shown that, for an efficient photochemical oxidation, the metal-centered, antibonding MOs must be energetically proximate to ligand-centered, bonding MOs. With this background, it is argued that the rare and unstable Ag(II) ion is uniquely positioned as an ideal candidate for LMCT photochemistry. A brief history of the inorganic chemistry of Ag(II) is presented, and the anticipated challenges with taming it for photochemical purposes are discussed. This chapter concludes with an extended discussion on energy balance in photoredox catalysis, and it is shown that Ag(II)-mediated LMCT, if realized, may possess properties beneficial for efficient photon utilization. In Chapter 2, synthetic routes toward well-defined mononuclear Ag(II) complexes are presented. With these complexes in hand, their proclivity toward LMCT photochemistry was investigated with trifluoroacetate (TFA) as the model substrate. With an oxidation potential exceeding 2 V vs SCE, TFA had, at the inception of this project, never been activated before with visible light through either molecular outer-sphere or inner-sphere photoredox methods. Furthermore, the oxidation of TFA would yield trifluoromethyl radicals which could be harnessed for the trifluoromethylation of arenes, an important process in the pharmaceutical industry. It is shown that [Ag(bpy)2][OTf]2 (bpy = 2,2´-bipyridine; OTf = triflate) spontaneously binds TFA in solution, forming [Ag(bpy)2(TFA)][OTf] and Ag(bpy)(TFA)2. Both of these complexes undergo LMCT with relatively high quantum efficiency when irradiated with blue light, resulting in the release of carbon dioxide and trifluoromethyl radicals which were harnessed to forge C(sp2)–CF3 bonds. Generality was demonstrated with the substitution of TFA with pentafluoropropionate and heptafluorobutyrate which released CF2CF3 and CF2CF2CF3 radicals, respectively, when bound to Ag(II) under irradiation. This photoredox reaction was then rendered catalytic in silver by regenerating the Ag(II) complexes electrochemically during irradiation. Thus, electrophotocatalytic perfluoroalkylation of arenes with turnover numbers exceeding 20 was accomplished. This work marks the first entry of Ag(II) into the field of (electro)photocatalysis. In Chapter 3, the nascent field of Ag(II)-based photocatalysis is expanded by the synthesis and systematic study of [Ag(bpy)2(O2CCF2X)]+ and Ag(bpy)(O2CCF2X)2 complexes where X = F, CF3, Cl, Br, H, and CH3. This series of homologous complexes provided the rare opportunity to investigate how electronic and structural perturbation of the M–L core is manifested in the LMCT quantum efficiency. A dramatic effect of the X substituent was uncovered, with quantum yields spanning over 20% for the carboxylates tested. With this information in hand, electrophotocatalytic C(sp2)–CF2X functionalization was carried out on a suite of (hetero)arenes. Notably, the incorporation of CF2X groups beyond CF3 into arene scaffolds is underdeveloped due, in part, to the lack of CF2X group transfer reagents. This work allows for widely available but inert CF2X carboxylates to be employed directly for CF2X functionalization reactions, the importance of which is underscored by these groups’ utility as halogen-bond donors and bioisosteres. Thus far, Ag(II) electrophotocatalytic cycles have been shown in this dissertation to enable fluoroalkyl radical generation from redox-reticent fluoroalkyl carboxylates, enabling these inexpensive and readily accessible compounds to serve as fluoroalkyl radical sources. Absent from these schemes, however, is a dedicated role for Ag(I) besides simply serving as a precursor for Ag(II). Coupling Ag(I)’s diverse ground state reactivity with Ag(II)’s LMCT photochemistry would represent a fundamentally new reactivity paradigm with the potential to provide access to novel reactivity pathways and products beyond simple perfluoroalkylation. In Chapter 4, the first implementation of this strategy is presented. By exploiting stoichiometric Ag(I) disproportionation in an operationally simple undivided electrochemical cell, steady supplies of both Ag(II) and Ag(I) are ensured under low overall cell potentials. Under these conditions, Ag(II)-mediated production of CF2X (X = Cl, Br) radicals is coupled with Ag(I)-mediated activation of the aryl–CF2X radical addition product, ultimately leading to the formation of synthetically valuable acyl fluorides (aryl–COF). Furthermore, the developed experimental setup may be extended to related perfluoroalkylations, resulting in excellent yields of valuable products across an expanded scope of medicinally relevant heterocycles, drug-like substrates, and natural products. These reactions may be run on the benchtop, are tolerant of both water and air, and require no supporting electrolyte. Furthermore, the spent Ag can be quantitatively recovered at the end of perfluoroalkylation reactions and recycled with no loss in reaction efficiency. Chapter 5 details the ongoing and future work on Ag(II) photochemistry in the Nocera Laboratories. Topics of interest include aryl radical generation from both benzoic acids and aryltrifluoroborate salts. For the latter, it was found that these salts form ion-pairs with Ag(II) centers in contrast to direct binding. Thus, these systems provide the opportunity to study how the kinetics of electron transfer are modulated on the spectrum between inner- and outer-sphere SET.application/pdfenChemistryThesis or Dissertation2026-07-070000-0002-9359-9862