Mechanistic Insights into Homogeneous Electrocatalytic and Photocatalytic Hydrogen Evolution Catalyzed by High-Spin Ni(II) Complexes with S2N2-Type Tetradentate Ligands

Dachao Hong, Yuto Tsukakoshi, Hiroaki Kotani, Tomoya Ishizuka, Kei Ohkubo, Yoshihito Shiota, Kazunari Yoshizawa, Shunichi Fukuzumi, Takahiko Kojima

研究成果: ジャーナルへの寄稿記事

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We report homogeneous electrocatalytic and photocatalytic H2 evolution using two Ni(II) complexes with S2N2-type tetradentate ligands bearing two different sizes of chelate rings as catalysts. A Ni(II) complex with a five-membered SC2S-Ni chelate ring (1) exhibited higher activity than that with a six-membered SC3S-Ni chelate ring (2) in both electrocatalytic and photocatalytic H2 evolution despite both complexes showing the same reduction potentials. A stepwise reduction of the Ni center from Ni(II) to Ni(0) was observed in the electrochemical measurements; the first reduction is a pure electron transfer reaction to form a Ni(I) complex as confirmed by electron spin resonance measurements, and the second is a 1e-/1H+ proton-coupled electron transfer reaction to afford a putative Ni(II)-hydrido (NiII-H) species. We also clarified that Ni(II) complexes can act as homogeneous catalysts in the electrocatalytic H2 evolution, in which complex 1 exhibited higher reactivity than that of 2. In the photocatalytic system using [Ru(bpy)3]2+ as a photosensitizer and sodium ascorbate as a reductant, complex 1 with the five-membered chelate ring also showed higher catalytic activity than that of 2 with the six-membered chelate ring, although the rates of photoinduced electron-transfer processes were comparable. The Ni-H bond cleavage in the putative NiII-H intermediate should be involved in the rate-limiting step as evidenced by kinetic isotope effects observed in both photocatalytic and electrocatalytic H2 evolution. Kinetic analysis and density functional theory calculations indicated that the difference in H2 evolution activity between the two complexes was derived from that of activation barriers of the reactions between the NiII-H intermediates and proton, which is consistent with the fact that increase of proton concentration accelerates the H2 evolution.

元の言語英語
ページ(範囲)7180-7190
ページ数11
ジャーナルInorganic Chemistry
57
発行部数12
DOI
出版物ステータス出版済み - 6 18 2018

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Protons
Hydrogen
chelates
Ligands
ligands
Electrons
Bearings (structural)
hydrogen
rings
electron transfer
Catalysts
Kinetics
Photosensitizing Agents
Reducing Agents
Isotopes
Ascorbic Acid
Density functional theory
Paramagnetic resonance
protons
Catalyst activity

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

これを引用

Mechanistic Insights into Homogeneous Electrocatalytic and Photocatalytic Hydrogen Evolution Catalyzed by High-Spin Ni(II) Complexes with S2N2-Type Tetradentate Ligands. / Hong, Dachao; Tsukakoshi, Yuto; Kotani, Hiroaki; Ishizuka, Tomoya; Ohkubo, Kei; Shiota, Yoshihito; Yoshizawa, Kazunari; Fukuzumi, Shunichi; Kojima, Takahiko.

:: Inorganic Chemistry, 巻 57, 番号 12, 18.06.2018, p. 7180-7190.

研究成果: ジャーナルへの寄稿記事

Hong, Dachao ; Tsukakoshi, Yuto ; Kotani, Hiroaki ; Ishizuka, Tomoya ; Ohkubo, Kei ; Shiota, Yoshihito ; Yoshizawa, Kazunari ; Fukuzumi, Shunichi ; Kojima, Takahiko. / Mechanistic Insights into Homogeneous Electrocatalytic and Photocatalytic Hydrogen Evolution Catalyzed by High-Spin Ni(II) Complexes with S2N2-Type Tetradentate Ligands. :: Inorganic Chemistry. 2018 ; 巻 57, 番号 12. pp. 7180-7190.
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title = "Mechanistic Insights into Homogeneous Electrocatalytic and Photocatalytic Hydrogen Evolution Catalyzed by High-Spin Ni(II) Complexes with S2N2-Type Tetradentate Ligands",
abstract = "We report homogeneous electrocatalytic and photocatalytic H2 evolution using two Ni(II) complexes with S2N2-type tetradentate ligands bearing two different sizes of chelate rings as catalysts. A Ni(II) complex with a five-membered SC2S-Ni chelate ring (1) exhibited higher activity than that with a six-membered SC3S-Ni chelate ring (2) in both electrocatalytic and photocatalytic H2 evolution despite both complexes showing the same reduction potentials. A stepwise reduction of the Ni center from Ni(II) to Ni(0) was observed in the electrochemical measurements; the first reduction is a pure electron transfer reaction to form a Ni(I) complex as confirmed by electron spin resonance measurements, and the second is a 1e-/1H+ proton-coupled electron transfer reaction to afford a putative Ni(II)-hydrido (NiII-H) species. We also clarified that Ni(II) complexes can act as homogeneous catalysts in the electrocatalytic H2 evolution, in which complex 1 exhibited higher reactivity than that of 2. In the photocatalytic system using [Ru(bpy)3]2+ as a photosensitizer and sodium ascorbate as a reductant, complex 1 with the five-membered chelate ring also showed higher catalytic activity than that of 2 with the six-membered chelate ring, although the rates of photoinduced electron-transfer processes were comparable. The Ni-H bond cleavage in the putative NiII-H intermediate should be involved in the rate-limiting step as evidenced by kinetic isotope effects observed in both photocatalytic and electrocatalytic H2 evolution. Kinetic analysis and density functional theory calculations indicated that the difference in H2 evolution activity between the two complexes was derived from that of activation barriers of the reactions between the NiII-H intermediates and proton, which is consistent with the fact that increase of proton concentration accelerates the H2 evolution.",
author = "Dachao Hong and Yuto Tsukakoshi and Hiroaki Kotani and Tomoya Ishizuka and Kei Ohkubo and Yoshihito Shiota and Kazunari Yoshizawa and Shunichi Fukuzumi and Takahiko Kojima",
year = "2018",
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doi = "10.1021/acs.inorgchem.8b00881",
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T1 - Mechanistic Insights into Homogeneous Electrocatalytic and Photocatalytic Hydrogen Evolution Catalyzed by High-Spin Ni(II) Complexes with S2N2-Type Tetradentate Ligands

AU - Hong, Dachao

AU - Tsukakoshi, Yuto

AU - Kotani, Hiroaki

AU - Ishizuka, Tomoya

AU - Ohkubo, Kei

AU - Shiota, Yoshihito

AU - Yoshizawa, Kazunari

AU - Fukuzumi, Shunichi

AU - Kojima, Takahiko

PY - 2018/6/18

Y1 - 2018/6/18

N2 - We report homogeneous electrocatalytic and photocatalytic H2 evolution using two Ni(II) complexes with S2N2-type tetradentate ligands bearing two different sizes of chelate rings as catalysts. A Ni(II) complex with a five-membered SC2S-Ni chelate ring (1) exhibited higher activity than that with a six-membered SC3S-Ni chelate ring (2) in both electrocatalytic and photocatalytic H2 evolution despite both complexes showing the same reduction potentials. A stepwise reduction of the Ni center from Ni(II) to Ni(0) was observed in the electrochemical measurements; the first reduction is a pure electron transfer reaction to form a Ni(I) complex as confirmed by electron spin resonance measurements, and the second is a 1e-/1H+ proton-coupled electron transfer reaction to afford a putative Ni(II)-hydrido (NiII-H) species. We also clarified that Ni(II) complexes can act as homogeneous catalysts in the electrocatalytic H2 evolution, in which complex 1 exhibited higher reactivity than that of 2. In the photocatalytic system using [Ru(bpy)3]2+ as a photosensitizer and sodium ascorbate as a reductant, complex 1 with the five-membered chelate ring also showed higher catalytic activity than that of 2 with the six-membered chelate ring, although the rates of photoinduced electron-transfer processes were comparable. The Ni-H bond cleavage in the putative NiII-H intermediate should be involved in the rate-limiting step as evidenced by kinetic isotope effects observed in both photocatalytic and electrocatalytic H2 evolution. Kinetic analysis and density functional theory calculations indicated that the difference in H2 evolution activity between the two complexes was derived from that of activation barriers of the reactions between the NiII-H intermediates and proton, which is consistent with the fact that increase of proton concentration accelerates the H2 evolution.

AB - We report homogeneous electrocatalytic and photocatalytic H2 evolution using two Ni(II) complexes with S2N2-type tetradentate ligands bearing two different sizes of chelate rings as catalysts. A Ni(II) complex with a five-membered SC2S-Ni chelate ring (1) exhibited higher activity than that with a six-membered SC3S-Ni chelate ring (2) in both electrocatalytic and photocatalytic H2 evolution despite both complexes showing the same reduction potentials. A stepwise reduction of the Ni center from Ni(II) to Ni(0) was observed in the electrochemical measurements; the first reduction is a pure electron transfer reaction to form a Ni(I) complex as confirmed by electron spin resonance measurements, and the second is a 1e-/1H+ proton-coupled electron transfer reaction to afford a putative Ni(II)-hydrido (NiII-H) species. We also clarified that Ni(II) complexes can act as homogeneous catalysts in the electrocatalytic H2 evolution, in which complex 1 exhibited higher reactivity than that of 2. In the photocatalytic system using [Ru(bpy)3]2+ as a photosensitizer and sodium ascorbate as a reductant, complex 1 with the five-membered chelate ring also showed higher catalytic activity than that of 2 with the six-membered chelate ring, although the rates of photoinduced electron-transfer processes were comparable. The Ni-H bond cleavage in the putative NiII-H intermediate should be involved in the rate-limiting step as evidenced by kinetic isotope effects observed in both photocatalytic and electrocatalytic H2 evolution. Kinetic analysis and density functional theory calculations indicated that the difference in H2 evolution activity between the two complexes was derived from that of activation barriers of the reactions between the NiII-H intermediates and proton, which is consistent with the fact that increase of proton concentration accelerates the H2 evolution.

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M3 - Article

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EP - 7190

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

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