Direct Observation of a Hydrogen‐Bonding Assisted Quasi‐Reversible Superoxo/Peroxo Interconversion in a Heme Model
Abstract
The activation and reduction of molecular oxygen at transition metal centers are central to both enzymatic catalysis and energy conversion. Here, we report the first direct observation of a hydrogen-bonding-assisted, quasi-reversible superoxo (Fe III ─O 2 ˙ˉ)/peroxo (Fe III ─O 2 2 ˉ) redox couple in a heme model complex using conventional cyclic voltammetry. Urea groups installed in the second coordination sphere (SCS) of an iron-porphyrin (ααUrFe) form a hydrogen-bonding network that stabilizes the Fe III ─O 2 ˙ˉintermediate through interaction with a trapped water molecule. Spectroscopic studies and DFT calculations reveal that one-electron reduction of the low-spin end-on Fe III ─O 2 ˙ˉspecies generates a low-spin end-on Fe III ─O 2 2 ˉadduct with minimal structural reorganization. These findings provide the first synthetic demonstration of a biologically relevant end-on peroxo species stabilized by hydrogen-bonding "pull effect" in the SCS and highlight the critical role of second-sphere interactions in modulating O 2 activation pathways in bioinspired catalysts.
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BibTeX
@article{trapali2026direct,
title = {{Direct Observation of a Hydrogen‐Bonding Assisted Quasi‐Reversible Superoxo/Peroxo Interconversion in a Heme Model}},
author = {Adelais Trapali and Régis Guillot and Christian Herrero and Sylvain Bertaina and Athanassios Coutsolelos and Maylis Orio and Zakaria Halime},
journal = {Chemistry - A European Journal},
year = {2026},
month = sep,
doi = {10.1002/chem.71748},
url = {https://hal.science/hal-05768819v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Direct Observation of a Hydrogen‐Bonding Assisted Quasi‐Reversible Superoxo/Peroxo Interconversion in a Heme Model
AU - Adelais Trapali
AU - Régis Guillot
AU - Christian Herrero
AU - Sylvain Bertaina
AU - Athanassios Coutsolelos
AU - Maylis Orio
AU - Zakaria Halime
PY - 2026
DA - 2026/09/29
JO - Chemistry - A European Journal
DO - 10.1002/chem.71748
UR - https://hal.science/hal-05768819v1
AB - The activation and reduction of molecular oxygen at transition metal centers are central to both enzymatic catalysis and energy conversion. Here, we report the first direct observation of a hydrogen-bonding-assisted, quasi-reversible superoxo (Fe III ─O 2 ˙ˉ)/peroxo (Fe III ─O 2 2 ˉ) redox couple in a heme model complex using conventional cyclic voltammetry. Urea groups installed in the second coordination sphere (SCS) of an iron-porphyrin (ααUrFe) form a hydrogen-bonding network that stabilizes the Fe III ─O 2 ˙ˉintermediate through interaction with a trapped water molecule. Spectroscopic studies and DFT calculations reveal that one-electron reduction of the low-spin end-on Fe III ─O 2 ˙ˉspecies generates a low-spin end-on Fe III ─O 2 2 ˉadduct with minimal structural reorganization. These findings provide the first synthetic demonstration of a biologically relevant end-on peroxo species stabilized by hydrogen-bonding "pull effect" in the SCS and highlight the critical role of second-sphere interactions in modulating O 2 activation pathways in bioinspired catalysts.
SN - 0947-6539
SN - 1521-3765
ER -