| Factors that control catalytic two- versus four-electron reduction of dioxygen by copper complexes. | |
MedLine Citation:
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PMID: 22462521 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The selective two-electron reduction of O(2) by one-electron reductants such as decamethylferrocene (Fc*) and octamethylferrocene (Me(8)Fc) is efficiently catalyzed by a binuclear Cu(II) complex [Cu(II)(2)(LO)(OH)](2+) (D1) {LO is a binucleating ligand with copper-bridging phenolate moiety} in the presence of trifluoroacetic acid (HOTF) in acetone. The protonation of the hydroxide group of [Cu(II)(2)(LO)(OH)](2+) with HOTF to produce [Cu(II)(2)(LO)(OTF)](2+) (D1-OTF) makes it possible for this to be reduced by 2 equiv of Fc* via a two-step electron-transfer sequence. Reactions of the fully reduced complex [Cu(I)(2)(LO)](+) (D3) with O(2) in the presence of HOTF led to the low-temperature detection of the absorption spectra due to the peroxo complex [Cu(II)(2)(LO)(OO)] (D) and the protonated hydroperoxo complex [Cu(II)(2)(LO)(OOH)](2+) (D4). No further Fc* reduction of D4 occurs, and it is instead further protonated by HOTF to yield H(2)O(2) accompanied by regeneration of [Cu(II)(2)(LO)(OTF)](2+) (D1-OTF), thus completing the catalytic cycle for the two-electron reduction of O(2) by Fc*. Kinetic studies on the formation of Fc*(+) under catalytic conditions as well as for separate examination of the electron transfer from Fc* to D1-OTF reveal there are two important reaction pathways operating. One is a rate-determining second reduction of D1-OTF, thus electron transfer from Fc* to a mixed-valent intermediate [Cu(II)Cu(I)(LO)](2+) (D2), which leads to [Cu(I)(2)(LO)](+) that is coupled with O(2) binding to produce [Cu(II)(2)(LO)(OO)](+) (D). The other involves direct reaction of O(2) with the mixed-valent compound D2 followed by rapid Fc* reduction of a putative superoxo-dicopper(II) species thus formed, producing D. |
Authors:
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Shunichi Fukuzumi; Laleh Tahsini; Yong-Min Lee; Kei Ohkubo; Wonwoo Nam; Kenneth D Karlin |
Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't Date: 2012-04-12 |
Journal Detail:
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Title: Journal of the American Chemical Society Volume: 134 ISSN: 1520-5126 ISO Abbreviation: J. Am. Chem. Soc. Publication Date: 2012 Apr |
Date Detail:
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Created Date: 2012-06-14 Completed Date: 2012-09-12 Revised Date: 2013-06-26 |
Medline Journal Info:
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Nlm Unique ID: 7503056 Medline TA: J Am Chem Soc Country: United States |
Other Details:
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Languages: eng Pagination: 7025-35 Citation Subset: IM |
Affiliation:
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Department of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea. fukuzumi@chem.eng.osaka-u.ac.jp |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Catalysis Copper / chemistry* Electrons* Hydrogen Peroxide / chemical synthesis, chemistry Molecular Structure Organometallic Compounds / chemistry* Oxidation-Reduction Oxygen / chemistry* Quantum Theory |
| Grant Support | |
ID/Acronym/Agency:
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GM28962/GM/NIGMS NIH HHS; R01 GM028962/GM/NIGMS NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Organometallic Compounds; 7440-50-8/Copper; 7722-84-1/Hydrogen Peroxide; 7782-44-7/Oxygen |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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