Electrode initiated proton-coupled electron transfer to promote degradation of a nickel(<scp>ii</scp>) coordination complex

McCarthy, Brian D.; Donley, Carrie L.; Dempsey, Jillian L.

doi:10.1039/c5sc00476d

Cited by 57 publications

(84 citation statements)

References 63 publications

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“…Significant attention has been drawn to whether electrocatalysis in organic solvents is of homogeneous or heterogeneous nature. More specifically, several studies on similar dithiolene‐ or thiolate‐containing systems have shown that under reductive conditions a molecular catalyst may decompose to form a material which deposits on the surface of the electrode and is responsible for the catalytic performance . Several diagnostic criteria have been used to identify if a process is truly catalytic, most notably rinse tests in which the electrode, after a scan or a potential has been applied for a period of time, is transferred to a fresh solution containing only the acid.…”

Section: Discussionmentioning

confidence: 99%

Proton‐Reduction Reaction Catalyzed by Homoleptic Nickel–bis‐1,2‐dithiolate Complexes: Experimental and Theoretical Mechanistic Investigations

et al. 2017

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A series of homoleptic monoanionic nickel dithiolene complexes [Ni(bdt)2](NBu4), [Ni(tdt)2](NBu4), and [Ni(mnt)2](NBu4) containing the ligands benzene‐1,2‐dithiolate (bdt2−), toluene‐3,4‐dithiolate (tdt2−), and maleonitriledithiolate (mnt2−), respectively, were employed as electrocatalysts in the hydrogen‐evolution reaction with trifluoroacetic acid as the proton source in acetonitrile. All complexes are active catalysts with TONs reaching 113, 158, and 6 for [Ni(bdt)2](NBu4), [Ni(tdt)2](NBu4), and [Ni(mnt)2](NBu4), respectively. The Faradaic yield for the hydrogen evolution reaction reaches 88 % for 2−, which also displays the minimal overpotential requirement value (467 mV) within the series. Two pathways for H2 evolution can be hypothesized that differ in the sequence of protonation and reduction steps. DFT calculations are in agreement with experimental data and indicate that protonation at sulfur follows the reduction to the dianion. Hydrogen evolves from the direduced–diprotonated form via a highly distorted nickel hydride intermediate. The effects of acid strength and concentration in the hydrogen‐evolving mechanism are also discussed.

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Section: Discussionmentioning

confidence: 99%

Proton‐Reduction Reaction Catalyzed by Homoleptic Nickel–bis‐1,2‐dithiolate Complexes: Experimental and Theoretical Mechanistic Investigations

et al. 2017

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“…and Dempsey et al . have attributed similar observations to the vulnerability of Ni−S bonds, which leads to electrochemical degradation of the catalyst in acidic media . Under these conditions, the homogeneous catalyst may become a precursor for a heterogeneous catalyst.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic Characterisation of a Bio‐Inspired Ni‐Based Proton Reduction Catalyst Bearing a Pentadentate N₂S₃ Ligand with Improved Photocatalytic Activity

Gotico

Moonshiram

Liu

et al. 2020

Chemistry A European J

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Inspired by the sulfur‐rich environment found in active hydrogenase enzymes, a Ni‐based proton reduction catalyst with pentadentate N2S3 ligand was synthesised. When coupled with [Ru(bpy)3]2+ (bpy=2,2′‐bipyridine) as photosensitiser and ascorbate as electron donor in a 1:1 mixture of dimethylacetamide and aqueous ascorbic acid/ascorbate buffer, the catalyst showed improved photocatalytic activity compared with a homologous counterpart bearing a tetradentate N2S2 ligand. The mechanistic pathway of photoinduced hydrogen evolution was comprehensively analysed through optical transient absorption and time‐resolved X‐ray absorption spectroscopy, which revealed important electronic and structural changes in the catalytic system during photoirradiation. The NiII catalyst undergoes a photoinduced metal‐centred reduction to form a NiI intermediate with distorted square‐bipyramidal geometry. Further kinetic analyses revealed differences in charge‐separation dynamics between the pentadentate and tetradentate forms.

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“…[10] In recent years, researchers have begun to investigate these transformations, however, only a few examples have been reported. [10][11][12][13][14][15][16][17][18][19][20][21] These studies have included both molecular Ni and Co complexes that undergo degradation and have highlighted the susceptibility of complexes that contain C=N bonds, N-O bonds, and/or Ni-S bonds. While a number of examples of Fe-based H 2 -evolving catalysts have been reported, [22][23][24] including many Fe-hydrogenase mimics, [4,[25][26][27][28] occurs through hydrogenation of the Schiff-base ligands, [18] we targeted the Fe analogue.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and electrochemical characterization of a tridentate Schiff-base ligated Fe(II) complex

et al. 2016

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The structural and electronic properties of an Fe(II) Schiff-base complex, [Fe(N 2 S) 2 ][ClO 4 ] 2 (N 2 S = 2-pyridyl-N-(2'-methylthiophenyl)methylenimine), are described and compared to an analogous Ni(II) species known to degrade to a H 2-evolving electrocatalytic film. Although structurally similar, the two complexes exhibit stark differences in their electrochemical and optical properties, and decompose via different pathways under reducing potentials. At potentials negative of the Fe(II/I) reduction wave, the complex degrades to a species that weakly adsorbs to the electrode surface. Prolonged electrolysis leads to the deposition of an Fe-containing film on the electrode.

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Electrode initiated proton-coupled electron transfer to promote degradation of a nickel(ii) coordination complex

Abstract: Electrochemical analysis of a nickel compound that degrades permitted a peek into the decomposition mechanism.

Cited by 57 publications

References 63 publications

Proton‐Reduction Reaction Catalyzed by Homoleptic Nickel–bis‐1,2‐dithiolate Complexes: Experimental and Theoretical Mechanistic Investigations

Proton‐Reduction Reaction Catalyzed by Homoleptic Nickel–bis‐1,2‐dithiolate Complexes: Experimental and Theoretical Mechanistic Investigations

Spectroscopic Characterisation of a Bio‐Inspired Ni‐Based Proton Reduction Catalyst Bearing a Pentadentate N₂S₃ Ligand with Improved Photocatalytic Activity

Synthesis and electrochemical characterization of a tridentate Schiff-base ligated Fe(II) complex

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Electrode initiated proton-coupled electron transfer to promote degradation of a nickel(ii) coordination complex

Abstract: Electrochemical analysis of a nickel compound that degrades permitted a peek into the decomposition mechanism.

Cited by 57 publications

References 63 publications

Proton‐Reduction Reaction Catalyzed by Homoleptic Nickel–bis‐1,2‐dithiolate Complexes: Experimental and Theoretical Mechanistic Investigations

Proton‐Reduction Reaction Catalyzed by Homoleptic Nickel–bis‐1,2‐dithiolate Complexes: Experimental and Theoretical Mechanistic Investigations

Spectroscopic Characterisation of a Bio‐Inspired Ni‐Based Proton Reduction Catalyst Bearing a Pentadentate N2S3 Ligand with Improved Photocatalytic Activity

Synthesis and electrochemical characterization of a tridentate Schiff-base ligated Fe(II) complex

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Spectroscopic Characterisation of a Bio‐Inspired Ni‐Based Proton Reduction Catalyst Bearing a Pentadentate N₂S₃ Ligand with Improved Photocatalytic Activity