67. Iridium Polypyridyl Carboxylates as Excited-State PCET Catalysts for the Functionalization of Unactivated C−H Bonds

Diego A. Granados, Y. Emily Du, Shiloh J. Andersson, Avery Cirincione-Lynch, Kai Cui, Adam Reinhold, Philip D. Jeffrey, Gregory D. Scholes, Sharon Hammes-Schiffer, Robert R. Knowles

J. Am. Chem. Soc. 2025, ASAP. DOI: 10.1021/jacs.5c04000

https://pubs.acs.org/doi/10.1021/jacs.5c04000

Abstract: The design of catalysts capable of functionalizing unactivated C(sp³)−H bonds remains a significant goal in synthetic organic chemistry. Herein, we present a novel set of iridium polypyridyl complexes bearing pendent Brønsted basic carboxylates that become potent hydrogen atom abstraction catalysts upon visible light irradiation. Thermochemical and spectroscopic characterization reveal that these excited-state complexes exhibit bond dissociation free energies (BDFEs) of up to 105 kcal mol⁻¹ with long excited-state lifetimes. We demonstrate that these complexes can catalyze C−H alkylation reactions in which the Ir carboxylate mediates both C−H abstraction and formation steps. Mechanistic, spectroscopic, and computational studies are consistent with C−H abstraction proceeding through an excited-state proton-coupled electron transfer (PCET) step. The modular nature of these Ir polypyridyl complexes establishes a foundation for designing tunable and efficient C−H functionalization catalysts based on covalent tethering of excited-state oxidants and bases.