Photochemical and thermal hydrogen production from water catalyzed by carboxylate-bridged dirhodium(ii) complexes

Saya Tanaka, Shigeyuki Masaoka, Kosei Yamauchi, Masahiko Annaka, Ken Sakai

研究成果: ジャーナルへの寄稿記事

33 引用 (Scopus)

抄録

A series of dinuclear Rh(ii) complexes, [Rh2(μ-OAc) 4(H2O)2] (HOAc = acetic acid) (1), [Rh 2(μ-gly)4(H2O)2] (Hgly = glycolic acid) (2), [Rh2(μ-CF3CO2) 4(acetone)2] (3), and [Rh2(bpy) 2(μ-OAc)2(OAc)2] (4), were found to serve as H2-evolving catalysts in a three-component system consisting of tris(2,2′-bipyridine)ruthenium(ii) (Ru(bpy)32+), methylviologen (MV2+), and ethylenediaminetetraacetic acid disodium salt (EDTA). It was also confirmed that thermal reduction of water into H 2 by MV+, in situ generated by the bulk electrolysis of MV2+, is effectively promoted by 1 as a H2-evolving catalyst. The absorption spectra of the photolysis solution during the photocatalysis were monitored up to 6 h to reveal that the formation of photochemical or thermal byproducts of MV+ is dramatically retarded in the presence of the Rh(ii)2 catalysts, for the H2 formation rather than the decomposition of MV+ becomes predominant in the presence of the Rh(ii)2 catalysts. The stability of the Rh(ii)2 dimers was confirmed by absorption spectroscopy, 1H NMR, and ESI-TOF mass spectroscopy. The results indicated that neither elimination nor replacement of the equatorial ligands take place during the photolysis, revealing that one of the axial sites of the Rh2 core is responsible for the hydrogenic activation. The quenching of Ru*(bpy)32+ by 1 was also investigated by luminescence spectroscopy. The rate of H2 evolution was found to decrease upon increasing the concentration of 1, indicating that the quenching of Ru*(bpy)32+ by the Rh(ii)2 species rather than by MV2+ becomes predominant at the higher concentrations of 1. The DFT calculations were carried out for several possible reaction paths proposed (e.g., [RhII2(μ-OAc)4(H 2O)] + H+ and [RhII2(μ-OAc) 4(H2O)] + H+ + e-). It is suggested that the initial step is a proton-coupled electron transfer (PCET) to the Rh(ii)2 dimer leading to the formation of a Rh(ii)Rh(iii)-H intermediate. The H2 evolution step is suggested to proceed either via the transfer of another set of H+ and e- to the Rh(ii)Rh(iii)-H intermediate or via the homolytic radical coupling through the interaction of two Rh(ii)Rh(iii)-H intermediates.

元の言語英語
ページ(範囲)11218-11226
ページ数9
ジャーナルDalton Transactions
39
発行部数46
DOI
出版物ステータス出版済み - 12 14 2010

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Hydrogen production
Catalysts
glycolic acid
Water
glycyl-glycyl-glycyl-glycine
Photolysis
Dimers
Quenching
Spectroscopy
Ruthenium
Photocatalysis
Acetone
Absorption spectroscopy
Electrolysis
Discrete Fourier transforms
Edetic Acid
Acetic Acid
Byproducts
Protons
Luminescence

All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

これを引用

Photochemical and thermal hydrogen production from water catalyzed by carboxylate-bridged dirhodium(ii) complexes. / Tanaka, Saya; Masaoka, Shigeyuki; Yamauchi, Kosei; Annaka, Masahiko; Sakai, Ken.

:: Dalton Transactions, 巻 39, 番号 46, 14.12.2010, p. 11218-11226.

研究成果: ジャーナルへの寄稿記事

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abstract = "A series of dinuclear Rh(ii) complexes, [Rh2(μ-OAc) 4(H2O)2] (HOAc = acetic acid) (1), [Rh 2(μ-gly)4(H2O)2] (Hgly = glycolic acid) (2), [Rh2(μ-CF3CO2) 4(acetone)2] (3), and [Rh2(bpy) 2(μ-OAc)2(OAc)2] (4), were found to serve as H2-evolving catalysts in a three-component system consisting of tris(2,2′-bipyridine)ruthenium(ii) (Ru(bpy)32+), methylviologen (MV2+), and ethylenediaminetetraacetic acid disodium salt (EDTA). It was also confirmed that thermal reduction of water into H 2 by MV+, in situ generated by the bulk electrolysis of MV2+, is effectively promoted by 1 as a H2-evolving catalyst. The absorption spectra of the photolysis solution during the photocatalysis were monitored up to 6 h to reveal that the formation of photochemical or thermal byproducts of MV+ is dramatically retarded in the presence of the Rh(ii)2 catalysts, for the H2 formation rather than the decomposition of MV+ becomes predominant in the presence of the Rh(ii)2 catalysts. The stability of the Rh(ii)2 dimers was confirmed by absorption spectroscopy, 1H NMR, and ESI-TOF mass spectroscopy. The results indicated that neither elimination nor replacement of the equatorial ligands take place during the photolysis, revealing that one of the axial sites of the Rh2 core is responsible for the hydrogenic activation. The quenching of Ru*(bpy)32+ by 1 was also investigated by luminescence spectroscopy. The rate of H2 evolution was found to decrease upon increasing the concentration of 1, indicating that the quenching of Ru*(bpy)32+ by the Rh(ii)2 species rather than by MV2+ becomes predominant at the higher concentrations of 1. The DFT calculations were carried out for several possible reaction paths proposed (e.g., [RhII2(μ-OAc)4(H 2O)] + H+ and [RhII2(μ-OAc) 4(H2O)] + H+ + e-). It is suggested that the initial step is a proton-coupled electron transfer (PCET) to the Rh(ii)2 dimer leading to the formation of a Rh(ii)Rh(iii)-H intermediate. The H2 evolution step is suggested to proceed either via the transfer of another set of H+ and e- to the Rh(ii)Rh(iii)-H intermediate or via the homolytic radical coupling through the interaction of two Rh(ii)Rh(iii)-H intermediates.",
author = "Saya Tanaka and Shigeyuki Masaoka and Kosei Yamauchi and Masahiko Annaka and Ken Sakai",
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T1 - Photochemical and thermal hydrogen production from water catalyzed by carboxylate-bridged dirhodium(ii) complexes

AU - Tanaka, Saya

AU - Masaoka, Shigeyuki

AU - Yamauchi, Kosei

AU - Annaka, Masahiko

AU - Sakai, Ken

PY - 2010/12/14

Y1 - 2010/12/14

N2 - A series of dinuclear Rh(ii) complexes, [Rh2(μ-OAc) 4(H2O)2] (HOAc = acetic acid) (1), [Rh 2(μ-gly)4(H2O)2] (Hgly = glycolic acid) (2), [Rh2(μ-CF3CO2) 4(acetone)2] (3), and [Rh2(bpy) 2(μ-OAc)2(OAc)2] (4), were found to serve as H2-evolving catalysts in a three-component system consisting of tris(2,2′-bipyridine)ruthenium(ii) (Ru(bpy)32+), methylviologen (MV2+), and ethylenediaminetetraacetic acid disodium salt (EDTA). It was also confirmed that thermal reduction of water into H 2 by MV+, in situ generated by the bulk electrolysis of MV2+, is effectively promoted by 1 as a H2-evolving catalyst. The absorption spectra of the photolysis solution during the photocatalysis were monitored up to 6 h to reveal that the formation of photochemical or thermal byproducts of MV+ is dramatically retarded in the presence of the Rh(ii)2 catalysts, for the H2 formation rather than the decomposition of MV+ becomes predominant in the presence of the Rh(ii)2 catalysts. The stability of the Rh(ii)2 dimers was confirmed by absorption spectroscopy, 1H NMR, and ESI-TOF mass spectroscopy. The results indicated that neither elimination nor replacement of the equatorial ligands take place during the photolysis, revealing that one of the axial sites of the Rh2 core is responsible for the hydrogenic activation. The quenching of Ru*(bpy)32+ by 1 was also investigated by luminescence spectroscopy. The rate of H2 evolution was found to decrease upon increasing the concentration of 1, indicating that the quenching of Ru*(bpy)32+ by the Rh(ii)2 species rather than by MV2+ becomes predominant at the higher concentrations of 1. The DFT calculations were carried out for several possible reaction paths proposed (e.g., [RhII2(μ-OAc)4(H 2O)] + H+ and [RhII2(μ-OAc) 4(H2O)] + H+ + e-). It is suggested that the initial step is a proton-coupled electron transfer (PCET) to the Rh(ii)2 dimer leading to the formation of a Rh(ii)Rh(iii)-H intermediate. The H2 evolution step is suggested to proceed either via the transfer of another set of H+ and e- to the Rh(ii)Rh(iii)-H intermediate or via the homolytic radical coupling through the interaction of two Rh(ii)Rh(iii)-H intermediates.

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