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Issue 11, 2015
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Catalytic two-electron reduction of dioxygen catalysed by metal-free [14]triphyrin(2.1.1)

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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).

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

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Supplementary files

Article information


Submitted
08 Jul 2015
Accepted
02 Aug 2015
First published
03 Aug 2015

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2015,6, 6496-6504
Article type
Edge Article
Author version available

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

K. Mase, K. Ohkubo, Z. Xue, H. Yamada and S. Fukuzumi, Chem. Sci., 2015, 6, 6496
DOI: 10.1039/C5SC02465J

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