Dual Catalytic Cycle of H2 and H2O Oxidations by a Half-Sandwich Iridium Complex: A Theoretical Study

研究成果: ジャーナルへの寄稿記事

抄録

While hydrogenase and photosystem II enzymes are known to oxidize H2 and H2O, respectively, a recently reported iridium aqua complex [IrIII5-C5Me5){bpy(COOH)2}(H2O)]2+ is able to oxidize both of the molecules and generate energies as in the fuel and solar cells (Ogo et al. ChemCatChem 2017, 9, 4024-4028). To understand the mechanism behind such an interesting bifunctional catalyst, in the present study, we perform density functional theory (DFT) calculations on the dual catalytic cycle of H2 and H2O oxidations by the iridium aqua complex. In the H2 oxidation, we found that the H-H bond is easily cleaved in a heterolytic fashion, and the resultant iridium hydride complex is significantly stabilized by the presence of H2O molecules, due to dihydrogen bond. The rate-determining step of this reaction is found to be the H2O → H2 ligand substitution with an activation energy of 10.7 kcal/mol. In the H2O oxidation, an iridium oxo complex originating from an oxidation of the iridium aqua complex forms a hydroperoxide complex, where an O-O bond is formed with an activation energy of 21.0 kcal/mol. Such a relatively low activation barrier is possible only when at least two H2O molecules are present in the reaction, allowing the water nucleophilic attack (WNA) mechanism to take place. The present study suggests and discusses in detail six reaction steps required for the dual catalytic cycle to complete.

元の言語英語
ページ(範囲)7274-7284
ページ数11
ジャーナルInorganic Chemistry
58
発行部数11
DOI
出版物ステータス出版済み - 6 3 2019

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Iridium
iridium
Oxidation
oxidation
cycles
Molecules
Activation energy
activation energy
molecules
Photosystem II Protein Complex
Hydrides
Hydrogen Peroxide
attack
fuel cells
hydrides
Density functional theory
enzymes
Fuel cells
Solar cells
Substitution reactions

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

これを引用

Dual Catalytic Cycle of H2 and H2O Oxidations by a Half-Sandwich Iridium Complex : A Theoretical Study. / Ikeda, Kei; Hori, Yuta; Mahyuddin, Muhammad Haris; Shiota, Yoshihito; Staykov, Aleksandar Tsekov; Matsumoto, Takahiro; Yoshizawa, Kazunari; Ogo, Seiji.

:: Inorganic Chemistry, 巻 58, 番号 11, 03.06.2019, p. 7274-7284.

研究成果: ジャーナルへの寄稿記事

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abstract = "While hydrogenase and photosystem II enzymes are known to oxidize H2 and H2O, respectively, a recently reported iridium aqua complex [IrIII(η5-C5Me5){bpy(COOH)2}(H2O)]2+ is able to oxidize both of the molecules and generate energies as in the fuel and solar cells (Ogo et al. ChemCatChem 2017, 9, 4024-4028). To understand the mechanism behind such an interesting bifunctional catalyst, in the present study, we perform density functional theory (DFT) calculations on the dual catalytic cycle of H2 and H2O oxidations by the iridium aqua complex. In the H2 oxidation, we found that the H-H bond is easily cleaved in a heterolytic fashion, and the resultant iridium hydride complex is significantly stabilized by the presence of H2O molecules, due to dihydrogen bond. The rate-determining step of this reaction is found to be the H2O → H2 ligand substitution with an activation energy of 10.7 kcal/mol. In the H2O oxidation, an iridium oxo complex originating from an oxidation of the iridium aqua complex forms a hydroperoxide complex, where an O-O bond is formed with an activation energy of 21.0 kcal/mol. Such a relatively low activation barrier is possible only when at least two H2O molecules are present in the reaction, allowing the water nucleophilic attack (WNA) mechanism to take place. The present study suggests and discusses in detail six reaction steps required for the dual catalytic cycle to complete.",
author = "Kei Ikeda and Yuta Hori and Mahyuddin, {Muhammad Haris} and Yoshihito Shiota and Staykov, {Aleksandar Tsekov} and Takahiro Matsumoto and Kazunari Yoshizawa and Seiji Ogo",
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T1 - Dual Catalytic Cycle of H2 and H2O Oxidations by a Half-Sandwich Iridium Complex

T2 - A Theoretical Study

AU - Ikeda, Kei

AU - Hori, Yuta

AU - Mahyuddin, Muhammad Haris

AU - Shiota, Yoshihito

AU - Staykov, Aleksandar Tsekov

AU - Matsumoto, Takahiro

AU - Yoshizawa, Kazunari

AU - Ogo, Seiji

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AB - While hydrogenase and photosystem II enzymes are known to oxidize H2 and H2O, respectively, a recently reported iridium aqua complex [IrIII(η5-C5Me5){bpy(COOH)2}(H2O)]2+ is able to oxidize both of the molecules and generate energies as in the fuel and solar cells (Ogo et al. ChemCatChem 2017, 9, 4024-4028). To understand the mechanism behind such an interesting bifunctional catalyst, in the present study, we perform density functional theory (DFT) calculations on the dual catalytic cycle of H2 and H2O oxidations by the iridium aqua complex. In the H2 oxidation, we found that the H-H bond is easily cleaved in a heterolytic fashion, and the resultant iridium hydride complex is significantly stabilized by the presence of H2O molecules, due to dihydrogen bond. The rate-determining step of this reaction is found to be the H2O → H2 ligand substitution with an activation energy of 10.7 kcal/mol. In the H2O oxidation, an iridium oxo complex originating from an oxidation of the iridium aqua complex forms a hydroperoxide complex, where an O-O bond is formed with an activation energy of 21.0 kcal/mol. Such a relatively low activation barrier is possible only when at least two H2O molecules are present in the reaction, allowing the water nucleophilic attack (WNA) mechanism to take place. The present study suggests and discusses in detail six reaction steps required for the dual catalytic cycle to complete.

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SN - 0020-1669

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