Document Detail


Factors that control catalytic two- versus four-electron reduction of dioxygen by copper complexes.
MedLine Citation:
PMID:  22462521     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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:
Shunichi Fukuzumi; Laleh Tahsini; Yong-Min Lee; Kei Ohkubo; Wonwoo Nam; Kenneth D Karlin
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-04-12
Journal Detail:
Title:  Journal of the American Chemical Society     Volume:  134     ISSN:  1520-5126     ISO Abbreviation:  J. Am. Chem. Soc.     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-06-14     Completed Date:  2012-09-12     Revised Date:  2013-06-26    
Medline Journal Info:
Nlm Unique ID:  7503056     Medline TA:  J Am Chem Soc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  7025-35     Citation Subset:  IM    
Affiliation:
Department of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea. fukuzumi@chem.eng.osaka-u.ac.jp
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MeSH Terms
Descriptor/Qualifier:
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:
GM28962/GM/NIGMS NIH HHS; R01 GM028962/GM/NIGMS NIH HHS
Chemical
Reg. No./Substance:
0/Organometallic Compounds; 7440-50-8/Copper; 7722-84-1/Hydrogen Peroxide; 7782-44-7/Oxygen
Comments/Corrections

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