Leveraging Multiproton-Coupled Electron Transfer to Improve Ir(III) Photocatalyst Efficiency

Villalona, Eris [Princeton University, NJ (United States)]; Domínguez, Rodrigo E. [Arizona State University, Tempe, AZ (United States)]; Gonzalez Lopez, Edwin J. [Arizona State University, Tempe, AZ (United States)]; Guerra, Walter D. [Arizona State University, Tempe, AZ (United States)]; Heredia, Daniel A. [Universidad Nacional de Río Cuarto, Córdoba (Argentina)] (ORCID:0000000206673906); Khmelnitskiy, Anton Y. [Arizona State University, Tempe, AZ (United States)]; Oblinsky, Daniel G. [Princeton University, NJ (United States)] (ORCID:0000000174608260); Palacios, Yohana [Arizona State University, Tempe, AZ (United States)]; Moore, Thomas A. [Arizona State University, Tempe, AZ (United States)] (ORCID:0000000215777117); Scholes, Gregory D. [Princeton University, NJ (United States)]; Knowles, Robert R. [Princeton University, NJ (United States)] (ORCID:0000000310444900); Moore, Ana L. [Arizona State University, Tempe, AZ (United States)] (ORCID:0000000266539506)

doi:10.1021/acs.jpcc.5c08623

DOE OSTI · 3019808

Leveraging Multiproton-Coupled Electron Transfer to Improve Ir(III) Photocatalyst Efficiency

Villalona, Eris [Princeton University, NJ (United States)]·Domínguez, Rodrigo E. [Arizona State University, Tempe, AZ (United States)]·Gonzalez Lopez, Edwin J. [Arizona State University, Tempe, AZ (United States)]·Guerra, Walter D. [Arizona State University, Tempe, AZ (United States)]·Heredia, Daniel A. [Universidad Nacional de Río Cuarto, Córdoba (Argentina)] (ORCID:0000000206673906)·Khmelnitskiy, Anton Y. [Arizona State University, Tempe, AZ (United States)]·Oblinsky, Daniel G. [Princeton University, NJ (United States)] (ORCID:0000000174608260)·Palacios, Yohana [Arizona State University, Tempe, AZ (United States)]·Moore, Thomas A. [Arizona State University, Tempe, AZ (United States)] (ORCID:0000000215777117)·Scholes, Gregory D. [Princeton University, NJ (United States)]·Knowles, Robert R. [Princeton University, NJ (United States)] (ORCID:0000000310444900)·Moore, Ana L. [Arizona State University, Tempe, AZ (United States)] (ORCID:0000000266539506)

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Abstract

In photoredox reactions, charge recombination (CR) limits quantum yields, hindering the efficient conversion of light energy into catalytic activity. To address this, we drew inspiration from redox relays in photosystem II (PSII) and developed a new series of iridium(III) complexes featuring covalently attached benzimidazole-phenol-pyridine (BIP-Py) groups to facilitate intramolecular multiproton-coupled electron transfer (MPCET). Herein, we evaluate the effects of MPCET through an extended and well-defined hydrogen-bond network to improve photocatalytic activity and mitigate rapid charge recombination. Infrared spectroelectrochemistry reveals pyridine protonation upon phenol oxidation, while visible spectroelectrochemistry and transient absorption spectroscopy confirm the electro- and photochemical formation of chargeseparated states (CSS) involving oxidized BIP, resulting from intramolecular proton-coupled electron transfer (PCET). The application of the BIP-Py platform in a photocatalytic Nhydroxyphthalimide ester reduction reaction resulted in a ∼106-fold reduction in CR rate and a quantum yield enhancement of up to 157%. Our findings suggest that incorporating MPCET-based redox relays into photocatalyst frameworks is an effective strategy to enhance the efficiency of photocatalytic systems.

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Catalysts Charge transfer Photocatalysts Proton coupled electron transfer Redox reactions

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Villalona, Eris [Princeton University, NJ (United States)], Domínguez, Rodrigo E. [Arizona State University, Tempe, AZ (United States)], Gonzalez Lopez, Edwin J. [Arizona State University, Tempe, AZ (United States)], Guerra, Walter D. [Arizona State University, Tempe, AZ (United States)], Heredia, Daniel A. [Universidad Nacional de Río Cuarto, Córdoba (Argentina)] (ORCID:0000000206673906), Khmelnitskiy, Anton Y. [Arizona State University, Tempe, AZ (United States)], Oblinsky, Daniel G. [Princeton University, NJ (United States)] (ORCID:0000000174608260), Palacios, Yohana [Arizona State University, Tempe, AZ (United States)], Moore, Thomas A. [Arizona State University, Tempe, AZ (United States)] (ORCID:0000000215777117), Scholes, Gregory D. [Princeton University, NJ (United States)], Knowles, Robert R. [Princeton University, NJ (United States)] (ORCID:0000000310444900), Moore, Ana L. [Arizona State University, Tempe, AZ (United States)] (ORCID:0000000266539506). 2026-02-05. Leveraging Multiproton-Coupled Electron Transfer to Improve Ir(III) Photocatalyst Efficiency. https://doi.org/10.1021/acs.jpcc.5c08623

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