Understanding light-driven H<sub>2</sub> evolution through the electronic tuning of aminopyridine cobalt complexes

Call, Arnau; Franco, Federico; Kandoth, Noufal; Fernández, Sergio Gómez; González‐Béjar, María; Pérez‐Prieto, Julia; Luis, Josep M.; Lloret‐Fillol, Julio

doi:10.1039/c7sc04328g

Cited by 41 publications

(56 citation statements)

References 69 publications

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“…18 We previously studied the formation of similar Co I species under photo-and electrochemical conditions. 20,35 The formation of homocoupling products and the isotopic Dlabelling pattern observed, together with radical clock experiments support that the reaction proceeds via the formation of benzylic radical species. As explained above, the most likely pathway to form the benzylic radicals is by a HAT from [Co II -H] to the  carbon of the olefin.…”

Section: Conditions B)mentioning

confidence: 72%

Light-Driven Reduction of Aromatic Olefins in Aqueous Media Catalysed by Aminopyridine Cobalt Complexes.

Lloret‐Fillol¹,

Casadevall

Pascual³

et al. 2021

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A catalytic system based on earth-abundant elements that efficiently hydrogenates aryl olefins using visible light as driving-force and H2O as the sole hydrogen atoms source is reported. The catalytic system involves a robust and well-defined aminopyridine cobalt complex and a heteroleptic Cu photoredox catalyst. The system shows the reduction of styrene in aqueous media with a remarkable selectivity (> 20000) versus water reduction (WR). Reactivity and mechanistic studies support the formation of a [Co-H] intermediate, which reacts as a hydrogen transfer agent (HAT). Synthetically useful deuterium-labelled compounds can be straightforwardly obtained by replacing H2O with D2O and using only catalysts based on earth-abundant elements. Moreover, the dual photocatalytic system and the photocatalytic conditions can be rationally designed to tune the selectivity for aryl olefin vs aryl ketone reduction; not only by changing the structural and electronic properties of the cobalt catalysts, but also by modifying the reduction properties of the light-harvesting system.

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Section: Conditions B)mentioning

confidence: 72%

Light-Driven Reduction of Aromatic Olefins in Aqueous Media Catalysed by Aminopyridine Cobalt Complexes.

Lloret‐Fillol¹,

Casadevall

Pascual³

et al. 2021

Preprint

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“…Synthe-ses of ligands L H and L Me and ligand precursors have been based or adapted from reported procedures in the literature. [14] Detailed synthetic procedures and characterization data can be found in section 1 of the SI.…”

Section: Experimental Section General Methods and Materialsmentioning

confidence: 99%

“…[13] The synthesis of the C 2 -symmetric chiral triamine was recently reported by Pericàs and co-workers. [14] Cobalt complexes Co H and Co Me were synthesized following the scheme in Figure 2 and fully characterized (section 1 in the SI). The 1 H-NMR spectra of the two complexes showed strong paramagnetic character, with broad signals in the spectral window between À 100 and 300 ppm, which is prototypical for a high-spin Co II (d 7 ) complex.…”

Section: Synthesis and Characterizationmentioning

confidence: 99%

The Dual Effect of Coordinating −NH Groups and Light in the Electrochemical CO₂ Reduction with Pyridylamino Co Complexes

et al. 2021

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Dedicated to JM Savéant for his pioneering work on molecular electrochemistry. CO 2 electroreduction could be improved by applying conceptualized strategies to overcome catalytic bottlenecks. In this regard, we report two new cobalt(II) complexes [Co-(Py 2 R N 3 )(OTf)](OTf) (Co R , R=H, Me) based on a new C 2 -symmetric pentacoordinate chiral ligand that are active on the electrochemical CO 2 reduction to CO. One of the complexes has a NÀ H group oriented towards the CO 2 binding site (Co H ), while the other has a NÀ Me group with the same orientation (Co Me ), as showed by X-ray diffraction. We have studied the effect of introducing hydrogen bonding sites, i. e. NÀ H in Co H , as a strategy to stabilize reaction intermediates. The complex bearing coordinating unprotected NÀ H group (Co H ) displays catalytic CO 2 reduction at the Co II/I redox potential (À 1.9 V vs. Fc, ca. 40 % FY CO ) whereas Co Me shows CO 2 reduction at the Co I/0 redox pair. FTIR-SEC and DFT calculations identified a [Co I À CO] + cation as catalytic intermediate. The beneficial effect of the NÀ H group has been attributed to the stabilization of reaction intermediates or transition states and by the larger electrondonating capacity, thus enhancing the nucleophilic character of the Co I intermediate. The study also points to the CO dissociation from the Co(I)À CO resting state intermediate as one of the bottlenecks of the catalytic cycle, which can be overcome with light irradiation, resulting in an increase of the total CO production (À 1.9 V, 81 % FY CO , 11.2 TON CO ) at the Co II/I redox potential.

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“…Recent efforts have led to the identification of various metal complexes as molecular HER catalysts . However, most of catalysts have limited aqueous solubility and require the use of organic solvents and extra organic acids to provide protons.…”

Section: Figurementioning

confidence: 99%

Water‐Soluble Polymers with Appending Porphyrins as Bioinspired Catalysts for the Hydrogen Evolution Reaction

et al. 2020

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Molecular design to improve catalyst performance is significant but challenging. In enzymes, residue groups that are close to reaction centers play critical roles in regulating activities. Using this bioinspired strategy, three water‐soluble polymers were designed with appending Co porphyrins and different side‐chain groups to mimic enzyme reaction centers and activity‐controlling residue groups, respectively. With these polymers, high hydrogen evolution efficiency was achieved in neutral aqueous media for electro‐ (turnover frequency >2.3×104 s−1) and photocatalysis (turnover number >2.7×104). Porphyrin units are surrounded and protected by polymer chains, and more importantly, the activity can be tuned with different side‐chain groups. Therefore, instead of revising molecular structures that is difficult from both design and synthesis points of view, polymers can be used to improve molecular solubility and stability and simultaneously regulate activity by using side‐chain groups.

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Understanding light-driven H₂ evolution through the electronic tuning of aminopyridine cobalt complexes

Abstract: Electronic effects provide a general mechanistic scenario for rationalizing photocatalytic water reduction activity with aminopyridine cobalt complexes.

Cited by 41 publications

References 69 publications

Light-Driven Reduction of Aromatic Olefins in Aqueous Media Catalysed by Aminopyridine Cobalt Complexes.

Light-Driven Reduction of Aromatic Olefins in Aqueous Media Catalysed by Aminopyridine Cobalt Complexes.

The Dual Effect of Coordinating −NH Groups and Light in the Electrochemical CO₂ Reduction with Pyridylamino Co Complexes

Water‐Soluble Polymers with Appending Porphyrins as Bioinspired Catalysts for the Hydrogen Evolution Reaction

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Understanding light-driven H2 evolution through the electronic tuning of aminopyridine cobalt complexes

Abstract: Electronic effects provide a general mechanistic scenario for rationalizing photocatalytic water reduction activity with aminopyridine cobalt complexes.

Cited by 41 publications

References 69 publications

Light-Driven Reduction of Aromatic Olefins in Aqueous Media Catalysed by Aminopyridine Cobalt Complexes.

Light-Driven Reduction of Aromatic Olefins in Aqueous Media Catalysed by Aminopyridine Cobalt Complexes.

The Dual Effect of Coordinating −NH Groups and Light in the Electrochemical CO2 Reduction with Pyridylamino Co Complexes

Water‐Soluble Polymers with Appending Porphyrins as Bioinspired Catalysts for the Hydrogen Evolution Reaction

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Understanding light-driven H₂ evolution through the electronic tuning of aminopyridine cobalt complexes

The Dual Effect of Coordinating −NH Groups and Light in the Electrochemical CO₂ Reduction with Pyridylamino Co Complexes