Detection of the site protected 7-coordinate RuV = O species and its chemical reactivity to enable catalytic water oxidation

Pineda‐Galvan, Yuliana; Ravari, Alireza Karbakhsh; Shmakov, Sergei; Lifshits, Liubov M.; Kaveevivitchai, Nattawut; Thummel, Randolph P.; Pushkar, Yulia

doi:10.1016/j.jcat.2019.05.014

Cited by 26 publications

(44 citation statements)

References 36 publications

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“…Further addition of 3.0 equivalent CAN caused a new signal at g = 2.28, 2.09, and 1.85. These EPR signals of monomer 1 fit quite well with that reported in literature for Ru III and Ru V species (Pushkar et al, 2014;Erdman et al, 2017;Pineda-Galvan et al, 2019). With 1.0 equivalents of CAN, dimer 2 showed a signal at g = 2.28, 2.16, 1.84 of Ru III species ( Figure S28).…”

Section: Resultssupporting

confidence: 88%

Amphiphilic Oxo-Bridged Ruthenium “Green Dimer” for Water Oxidation

et al. 2020

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Section: Resultssupporting

confidence: 88%

Amphiphilic Oxo-Bridged Ruthenium “Green Dimer” for Water Oxidation

et al. 2020

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“… 47 It is also worth noting that such proposed Ir VI intermediates are isoelectronic to Ru V species, which are proposed to play important role in molecular OER catalysts. 27 , 52 − 54 …”

Section: Resultsmentioning

confidence: 99%

Atomically Dispersed Iridium on Indium Tin Oxide Efficiently Catalyzes Water Oxidation

et al. 2020

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Heterogeneous catalysts in the form of atomically dispersed metals on a support provide the most efficient utilization of the active component, which is especially important for scarce and expensive late transition metals. These catalysts also enable unique opportunities to understand reaction pathways through detailed spectroscopic and computational studies. Here, we demonstrate that atomically dispersed iridium sites on indium tin oxide prepared via surface organometallic chemistry display exemplary catalytic activity in one of the most challenging electrochemical processes, the oxygen evolution reaction (OER). In situ X-ray absorption studies revealed the formation of Ir V =O intermediate under OER conditions with an Ir–O distance of 1.83 Å. Modeling of the reaction mechanism indicates that Ir V =O is likely a catalyst resting state, which is subsequently oxidized to Ir VI enabling fast water nucleophilic attack and oxygen evolution. We anticipate that the applied strategy can be instrumental in preparing and studying a broad range of atomically dispersed transition metal catalysts on conductive oxides for (photo)electrochemical applications.

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“…Follow up spectroscopic experiments did not identify spectroscopic signatures of 2 in the reaction mixtures, suggesting that this species must be very short lived. Fe V (d 3 ) is isoelectronic to Ru V (d 3 ): the species which are also very short lived but can be observed in situ at selected conditions . Moreover, depending on the reaction conditions, Ru V =O species can form the O−O bond via both radical coupling (RC) and water nucleophilic attack (WNA) pathways .…”

Section: Figurementioning

confidence: 99%

Characterization of the Fe^V=O Complex in the Pathway of Water Oxidation

2020

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Hypervalent FeV=O species are implicated in a multitude of oxidative reactions of organic substrates, as well as in catalytic water oxidation, a reaction crucial for artificial photosynthesis. Spectroscopically characterized FeV species are exceedingly rare and, so far, were produced by the oxidation of Fe complexes with peroxy acids or H2O2: reactions that entail breaking of the O−O bond to form a FeV=O fragment. The key FeV=O species proposed to initiate the O−O bond formation in water oxidation reactions remained undetected, presumably due to their high reactivity. Here, we achieved freeze quench trapping of six coordinated [FeV=O,(OH)(Pytacn)]2+ (Pytacn=1‐(2′‐pyridylmethyl)‐4,7‐dimethyl‐1,4,7‐triazacyclononane) (2) generated during catalytic water oxidation. X‐ray absorption spectroscopy (XAS) confirmed the FeV oxidation state and the presence of a FeV=O bond at ≈1.60 Å. Combined EPR and DFT methods indicate that 2 contains a S=3/2 FeV center. 2 is the first spectroscopically characterized high spin oxo‐FeV complex and constitutes a paradigmatic example of the FeV=O(OH) species proposed to be responsible for catalytic water oxidation reactions.

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Detection of the site protected 7-coordinate RuV = O species and its chemical reactivity to enable catalytic water oxidation

Cited by 26 publications

References 36 publications

Amphiphilic Oxo-Bridged Ruthenium “Green Dimer” for Water Oxidation

Amphiphilic Oxo-Bridged Ruthenium “Green Dimer” for Water Oxidation

Atomically Dispersed Iridium on Indium Tin Oxide Efficiently Catalyzes Water Oxidation

Characterization of the Fe^V=O Complex in the Pathway of Water Oxidation

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Detection of the site protected 7-coordinate RuV = O species and its chemical reactivity to enable catalytic water oxidation

Cited by 26 publications

References 36 publications

Amphiphilic Oxo-Bridged Ruthenium “Green Dimer” for Water Oxidation

Amphiphilic Oxo-Bridged Ruthenium “Green Dimer” for Water Oxidation

Atomically Dispersed Iridium on Indium Tin Oxide Efficiently Catalyzes Water Oxidation

Characterization of the FeV=O Complex in the Pathway of Water Oxidation

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Detection of the site protected 7-coordinate RuV = O species and its chemical reactivity to enable catalytic water oxidation

Characterization of the Fe^V=O Complex in the Pathway of Water Oxidation