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Proton-Coupled Electron Transfer from the Hydride Perspective: Resolving Metal Oxidation and Protonation in a Hydridocarbonyl Complex by 2D-IR Spectroelectrochemistry

Published inThe Journal of Physical Chemistry Letters, vol. 17, no. 10, no. Future Leaders in Physical Chemistry, p. 3008-3012
Publication date2026-03-12
First online date2026-02-25
Abstract

Proton-coupled electron transfer (PCET) is a fundamental process in energy conversion and catalysis, yet direct spectroscopic characterization of metal hydride intermediates remains challenging. Here, we employ ultrafast two-dimensional infrared spectroelectrochemistry (2D-IR-SEC) to investigate the structural and vibrational dynamics of a model hydridocarbonyl complex, [HIrI(CO)(PPh3)3] (H1), during sequential oxidation and PCET reactions. The strong anharmonic coupling between the Ir-H and Ir(C≡O) stretching modes enables simultaneous monitoring of the metal oxidation state and hydride protonation state in real time. Spectroelectrochemical studies reveal that the first oxidation reversibly generates a stable 17-electron species. The second oxidation, in contrast, triggers irreversible PCET-driven deprotonation. 2D-IR-SEC spectra of the singly oxidized species show motional narrowing of the band with a stronger Ir-H character, reflecting altered solvation dynamics upon oxidation. This work thus establishes 2D-IR-SEC as a powerful tool for resolving coupled electron and proton transfer events in metal hydrides, with implications for the design of PCET-mediated catalysts.

Citation (ISO format)
FERNÁNDEZ-TERÁN, Ricardo José et al. Proton-Coupled Electron Transfer from the Hydride Perspective: Resolving Metal Oxidation and Protonation in a Hydridocarbonyl Complex by 2D-IR Spectroelectrochemistry. In: The Journal of Physical Chemistry Letters, 2026, vol. 17, n° 10, p. 3008–3012. doi: 10.1021/acs.jpclett.5c03977
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Additional URL for this publicationhttps://pubs.acs.org/doi/10.1021/acs.jpclett.5c03977
Journal ISSN1948-7185
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