Catalytic two-electron reduction of dioxygen catalysed by metal-free [14]triphyrin(2.1.1)

Kentaro Mase; Kei Ohkubo; Zhaoli Xue; Hiroko Yamada; Shunichi Fukuzumi

doi:10.1039/c5sc02465j

Catalytic two-electron reduction of dioxygen catalysed by metal-free [14]triphyrin(2.1.1)

Kentaro Mase, Kei Ohkubo, Zhaoli Xue, Hiroko Yamada, Shunichi Fukuzumi

Department of Chemistry & Nanoscience

Research output: Contribution to journal › Article › peer-review

32 Scopus citations

Abstract

The catalytic two-electron reduction of dioxygen (O₂) by octamethylferrocene (Me₈Fc) occurs with a metal-free triphyrin (HTrip) in the presence of perchloric acid (HClO₄) in benzonitrile (PhCN) at 298 K to yield Me₈Fc⁺ and H₂O₂. Detailed kinetic analysis has revealed that the catalytic two-electron reduction of O₂ by Me₈Fc with HTrip proceeds via proton-coupled electron transfer from Me₈Fc to HTrip to produce H₃Trip^•+, followed by a second electron transfer from Me₈Fc to H₃Trip^•+ to produce H₃Trip, which is oxidized by O₂via formation of the H₃Trip/O₂ complex to yield H₂O₂. The rate-determining step in the catalytic cycle is hydrogen atom transfer from H₃Trip to O₂ in the H₃Trip/O₂ complex to produce the radical pair (H₃Trip^•+ HO₂^•) as an intermediate, which was detected as a triplet EPR signal with fine-structure by the EPR measurements at low temperature. The distance between the two unpaired electrons in the radical pair was determined to be 4.9 Å from the zero-field splitting constant (D).

Original language	English
Pages (from-to)	6496-6504
Number of pages	9
Journal	Chemical Science
Volume	6
Issue number	11
DOIs	https://doi.org/10.1039/c5sc02465j
State	Published - 3 Aug 2015

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© The Royal Society of Chemistry.

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@article{1532e917a70049dca25e71f9313c9138,

title = "Catalytic two-electron reduction of dioxygen catalysed by metal-free [14]triphyrin(2.1.1)",

abstract = "The catalytic two-electron reduction of dioxygen (O2) by octamethylferrocene (Me8Fc) occurs with a metal-free triphyrin (HTrip) in the presence of perchloric acid (HClO4) in benzonitrile (PhCN) at 298 K to yield Me8Fc+ and H2O2. Detailed kinetic analysis has revealed that the catalytic two-electron reduction of O2 by Me8Fc with HTrip proceeds via proton-coupled electron transfer from Me8Fc to HTrip to produce H3Trip•+, followed by a second electron transfer from Me8Fc to H3Trip•+ to produce H3Trip, which is oxidized by O2via formation of the H3Trip/O2 complex to yield H2O2. The rate-determining step in the catalytic cycle is hydrogen atom transfer from H3Trip to O2 in the H3Trip/O2 complex to produce the radical pair (H3Trip•+ HO2•) as an intermediate, which was detected as a triplet EPR signal with fine-structure by the EPR measurements at low temperature. The distance between the two unpaired electrons in the radical pair was determined to be 4.9 {\AA} from the zero-field splitting constant (D).",

author = "Kentaro Mase and Kei Ohkubo and Zhaoli Xue and Hiroko Yamada and Shunichi Fukuzumi",

note = "Publisher Copyright: {\textcopyright} The Royal Society of Chemistry.",

year = "2015",

month = aug,

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doi = "10.1039/c5sc02465j",

language = "English",

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T1 - Catalytic two-electron reduction of dioxygen catalysed by metal-free [14]triphyrin(2.1.1)

AU - Mase, Kentaro

AU - Ohkubo, Kei

AU - Xue, Zhaoli

AU - Yamada, Hiroko

AU - Fukuzumi, Shunichi

PY - 2015/8/3

Y1 - 2015/8/3

N2 - The catalytic two-electron reduction of dioxygen (O2) by octamethylferrocene (Me8Fc) occurs with a metal-free triphyrin (HTrip) in the presence of perchloric acid (HClO4) in benzonitrile (PhCN) at 298 K to yield Me8Fc+ and H2O2. Detailed kinetic analysis has revealed that the catalytic two-electron reduction of O2 by Me8Fc with HTrip proceeds via proton-coupled electron transfer from Me8Fc to HTrip to produce H3Trip•+, followed by a second electron transfer from Me8Fc to H3Trip•+ to produce H3Trip, which is oxidized by O2via formation of the H3Trip/O2 complex to yield H2O2. The rate-determining step in the catalytic cycle is hydrogen atom transfer from H3Trip to O2 in the H3Trip/O2 complex to produce the radical pair (H3Trip•+ HO2•) as an intermediate, which was detected as a triplet EPR signal with fine-structure by the EPR measurements at low temperature. The distance between the two unpaired electrons in the radical pair was determined to be 4.9 Å from the zero-field splitting constant (D).

AB - The catalytic two-electron reduction of dioxygen (O2) by octamethylferrocene (Me8Fc) occurs with a metal-free triphyrin (HTrip) in the presence of perchloric acid (HClO4) in benzonitrile (PhCN) at 298 K to yield Me8Fc+ and H2O2. Detailed kinetic analysis has revealed that the catalytic two-electron reduction of O2 by Me8Fc with HTrip proceeds via proton-coupled electron transfer from Me8Fc to HTrip to produce H3Trip•+, followed by a second electron transfer from Me8Fc to H3Trip•+ to produce H3Trip, which is oxidized by O2via formation of the H3Trip/O2 complex to yield H2O2. The rate-determining step in the catalytic cycle is hydrogen atom transfer from H3Trip to O2 in the H3Trip/O2 complex to produce the radical pair (H3Trip•+ HO2•) as an intermediate, which was detected as a triplet EPR signal with fine-structure by the EPR measurements at low temperature. The distance between the two unpaired electrons in the radical pair was determined to be 4.9 Å from the zero-field splitting constant (D).

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U2 - 10.1039/c5sc02465j

DO - 10.1039/c5sc02465j

M3 - Article

AN - SCOPUS:84944051549

SN - 2041-6520

VL - 6

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EP - 6504

JO - Chemical Science

JF - Chemical Science

IS - 11

ER -

Catalytic two-electron reduction of dioxygen catalysed by metal-free [14]triphyrin(2.1.1)

Abstract

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