Researchers Isolate and Characterize Elusive Intermediate in Water Oxidation Reaction

The Water Oxidation Reaction (WOR) is considered one of the most essential reactions on the planet as it is the source of almost all the oxygen present in the air. Gaining insights into its intricacies could help enhance the efficiency of the reaction.

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Sadly, the mechanisms behind this reaction are complicated and the reaction intermediates are largely unstable, which makes isolating and characterizing them highly difficult. To resolve this issue, researchers have used molecular catalysts as models to comprehend the basic aspects of water oxidation—specifically the oxygen-oxygen bond-forming reaction.

Researchers from the Institute of Chemical Research of Catalonia (ICIQ)’s Lloret-Fillol group who have been closely studying WOR have, for the first time, isolated and completely characterized an elusive intermediate produced following the oxygen-oxygen bond formation event—the rate-determining step of the reaction.

The study is an international effort guided by ICIQ in collaboration with the University of Groningen (The Netherlands) and Synchrotron SOLEIL (France). It has been published in the Nature Chemistry journal.

Our work has direct implications in our capacity to look at the oxygen-oxygen bond formation step and the afterwards reaction intermediates.

Julio Lloret-Fillol, Study Lead Author, ICREA Professor, and Group Leader, Institute of Chemical Research of Catalonia

The researchers altered the conditions in their catalytic system to crystallize the Ru(IV) side-on peroxo produced following the reaction’s rate-determining step—the oxygen-oxygen bond formation event.

The paper will help to better understand the mechanism of the oxygen-oxygen bond formation, since it shows direct evidence for a single-site mechanism to form the oxygen-oxygen bond, one of the mechanisms postulated for photosystem II.

Carla Casadevall, Marie Skłodowska-Curie Postdoctoral Researcher, Erwin Reisner Group, University of Cambridge

Casadevall is the first author of the paper and former PhD student of the Lloret group.

In spite of comprehensive measures taken to clarify WOR’s mechanism, it is still not understood completely, prompting a continuing debate with numerous proposals regarding the mechanism of formation of the oxygen-oxygen bond.

The scientists have made use of labeling studies to track the intermediates formed both before and after the WOR’s rate-determining step. Therefore, the researchers have been capable of offering direct proof of the development of the oxygen-oxygen bond by water nucleophilic attack from the metal-oxo.

Journal Reference:

Casadevall, C., et al. (2021) Isolation of a Ru(IV) side-on peroxo intermediate in the water oxidation reaction. Nature Chemistry.


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