A molecular structural analog of proposed dinuclear active sites in cobalt-based water oxidation catalysts

Davenport, Timothy C.; Ahn, Hyun S.; Ziegler, Micah S.; Tilley, T. Don

doi:10.1039/c3cc46865h

Cited by 45 publications

(69 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…DFT calculations indicate that dicobalt centers like this may undergo O−O bond formation from the Co(IV)Co(IV) state, perhaps via deprotonation to an oxo−hydroxy intermediate. 31,42 Note that Siegbahn's DFT calculation indicates that a direct coupling mechanism of this type is less preferred in cubanes, by ∼3 kcal/ mol. 30 This complex mechanism was modeled numerically with global kinetics analysis, which successfully reproduced the initial rates, as well as the entire kinetic profile ( Figure 4C,D).…”

Section: Journal Of the American Chemical Societymentioning

confidence: 97%

Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation

et al. 2015

Self Cite

View full text Add to dashboard Cite

Artificial photosynthesis (AP) promises to replace society's dependence on fossil energy resources via conversion of sunlight into sustainable, carbon-neutral fuels. However, large-scale AP implementation remains impeded by a dearth of cheap, efficient catalysts for the oxygen evolution reaction (OER). Cobalt oxide materials can catalyze the OER and are potentially scalable due to the abundance of cobalt in the Earth's crust; unfortunately, the activity of these materials is insufficient for practical AP implementation. Attempts to improve cobalt oxide's activity have been stymied by limited mechanistic understanding that stems from the inherent difficulty of characterizing structure and reactivity at surfaces of heterogeneous materials. While previous studies on cobalt oxide revealed the intermediacy of the unusual Co(IV) oxidation state, much remains unknown, including whether bridging or terminal oxo ligands form O2 and what the relevant oxidation states are. We have addressed these issues by employing a homogeneous model for cobalt oxide, the [Co(III)4] cubane (Co4O4(OAc)4py4, py = pyridine, OAc = acetate), that can be oxidized to the [Co(IV)Co(III)3] state. Upon addition of 1 equiv of sodium hydroxide, the [Co(III)4] cubane is regenerated with stoichiometric formation of O2. Oxygen isotopic labeling experiments demonstrate that the cubane core remains intact during this stoichiometric OER, implying that terminal oxo ligands are responsible for forming O2. The OER is also examined with stopped-flow UV-visible spectroscopy, and its kinetic behavior is modeled, to surprisingly reveal that O2 formation requires disproportionation of the [Co(IV)Co(III)3] state to generate an even higher oxidation state, formally [Co(V)Co(III)3] or [Co(IV)2Co(III)2]. The mechanistic understanding provided by these results should accelerate the development of OER catalysts leading to increasingly efficient AP systems.

show abstract

Section: Journal Of the American Chemical Societymentioning

confidence: 97%

Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…Our findings furthermore illustrate the significant impact of "spectator" anions and buffer media on the catalytic efficiency, 34 such as the observed inhibitory effect of deprotonated phosphate donor ligands on the active sites of potential dinuclear Co-WOCs. 35 (3) Next, photocatalytic and computational results based on innovative Ln-containing Born-Oppenheimer MD provide the proof-of-principle for Ln 3+ centers as active catalytic promoters with flexible ligand binding modes in close analogy to OEC mechanisms. 15,24,36 A detailed investigation into subtle effects of the different Ln metal centers and the underlying mechanisms will be in the focus of further studies.…”

Section: Density Functional Theory-based Calculationsmentioning

confidence: 99%

3d–4f {Co^II₃Ln(OR)₄} Cubanes as Bio-Inspired Water Oxidation Catalysts

et al. 2015

View full text Add to dashboard Cite

Although the {CaMn4O5} oxygen evolving complex (OEC) of photosystem II is a major paradigm for water oxidation catalyst (WOC) development, the comprehensive translation of its key features into active molecular WOCs remains challenging. The [Co(II)3Ln(hmp)4(OAc)5H2O] ({Co(II)3Ln(OR)4}; Ln = Ho-Yb, hmp = 2-(hydroxymethyl)pyridine) cubane WOC series is introduced as a new springboard to address crucial design parameters, ranging from nuclearity and redox-inactive promoters to operational stability and ligand exchange properties. The {Co(II)3Ln(OR)4} cubanes promote bioinspired WOC design by newly combining Ln(3+) centers as redox-inactive Ca(2+) analogues with flexible aqua-/acetate ligands into active and stable WOCs (max. TON/TOF values of 211/9 s(-1)). Furthermore, they open up the important family of 3d-4f complexes for photocatalytic applications. The stability of the {Co(II)3Ln(OR)4} WOCs under photocatalytic conditions is demonstrated with a comprehensive analytical strategy including trace metal analyses and solution-based X-ray absorption spectroscopy (XAS) investigations. The productive influence of the Ln(3+) centers is linked to favorable ligand mobility, and the experimental trends are substantiated with Born-Oppenheimer molecular dynamics studies.

show abstract

“…23 Hence, this ligand can be found in both molecular and extended polymetallic systems, where it bridges two or more cationic centres. [24][25][26][27][28][29][30][31][32][33][34][35][36][37] As can be understood from the Cambridge Structural Database, CSD, 38 many first transition metal ion phosphates have been reported, but copper based systems are one of the most studied. Among the molecular complexes, the best known are the dinuclear copper phosphate bridged ones, while the tetranuclear and trinuclear species have been less investigated.…”

Section: Introductionmentioning

confidence: 99%

Models to predict the magnetic properties of single- and multiple-bridged phosphate Cu^II systems: a theoretical DFT insight

Muñoz‐Becerra

Aravena

Ruiz

et al. 2017

Inorg. Chem. Front.

View full text Add to dashboard Cite

show abstract

A molecular structural analog of proposed dinuclear active sites in cobalt-based water oxidation catalysts

Cited by 45 publications

References 24 publications

Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation

Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation

3d–4f {Co^II₃Ln(OR)₄} Cubanes as Bio-Inspired Water Oxidation Catalysts

Models to predict the magnetic properties of single- and multiple-bridged phosphate Cu^II systems: a theoretical DFT insight

Contact Info

Product

Resources

About

A molecular structural analog of proposed dinuclear active sites in cobalt-based water oxidation catalysts

Cited by 45 publications

References 24 publications

Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation

Mechanistic Investigations of Water Oxidation by a Molecular Cobalt Oxide Analogue: Evidence for a Highly Oxidized Intermediate and Exclusive Terminal Oxo Participation

3d–4f {CoII3Ln(OR)4} Cubanes as Bio-Inspired Water Oxidation Catalysts

Models to predict the magnetic properties of single- and multiple-bridged phosphate CuII systems: a theoretical DFT insight

Contact Info

Product

Resources

About

3d–4f {Co^II₃Ln(OR)₄} Cubanes as Bio-Inspired Water Oxidation Catalysts

Models to predict the magnetic properties of single- and multiple-bridged phosphate Cu^II systems: a theoretical DFT insight