Journal ArticleDOI
X-ray absorption edge determination of the oxidation state and coordination number of copper: application to the type 3 site in Rhus vernicifera laccase and its reaction with oxygen
Lung Shan Kau,Darlene J. Spira-Solomon,James E. Penner-Hahn,Keith O. Hodgson,Edward I. Solomon +4 more
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TLDR
In this paper, a normalized difference edge analysis is used to quantitatively determine the oxidation states of the copper sites in type 2 copper-depleted (T2D) and native forms of the multicopper oxidase, Rhus vernicifera laccase.Abstract:
Cu X-ray absorption edge features of 19 Cu(I) and 40 Cu(II) model complexes have been systematically studied and correlated with oxidation state and geometry. Studies of Cu(I) model complexes with different coordination number reveal that an 8983-8984-eV peak (assigned as the Cu 1s ..-->.. 4p transition) can be correlated in energy, shape, and intensity with ligation and site geometry of the cuprous ion. These Cu(I) edge features have been qualitatively interpreted with ligand field concepts. Alternatively, no Cu(II) complex exhibits a peak below 8985.0 eV. The limited intensity observed in the 8983-8985-eV region for some Cu(II) complexes is associated with the tail of an absorption peak at approx. 8986 eV which is affected by the covalency of the equatorial ligands. These models studies allow accurate calibration of a normalized difference edge procedure which is used for the quantitative determination of Cu(I) content in copper complexes of mixed oxidation state composition. This normalized difference edge analysis is then used to quantitatively determine the oxidation states of the copper sites in type 2 copper-depleted (T2D) and native forms of the multicopper oxidase, Rhus vernicifera laccase. The type 3 site of the T2D laccase is found to be fully reduced and stable tomore » oxidation by O/sub 2/ or by 25-fold protein equivalents of ferricyanide, but it can be oxidized by reaction with peroxide. The increase in intensity of the 330-nm absorption feature which results from peroxide titration of T2D laccase is found to correlate linearly with the percent of oxidation of the binuclear copper site.« lessread more
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Journal ArticleDOI
Cationic Copper Iminophosphorane Complexes as CuAAC Catalysts: A Mechanistic Study
Bas Venderbosch,Jean-Pierre H. Oudsen,Jarl Ivar van der Vlugt,Ties J. Korstanje,Moniek Tromp,Moniek Tromp +5 more
TL;DR: In this article, the authors combined X-ray absorption spectroscopy with NMR spectrograms to study the Cu-catalyzed azide-alkyne cycloaddition (CuAC) reaction under operando conditions.
Journal ArticleDOI
Structural characterisation of copper-containing manganese oxide octahedral molecular sieve (Cu-OMS-2) materials by X-ray absorption spectroscopy and cyclic voltammetry
TL;DR: In this article, the results from X-ray absorption spectroscopy have been interpreted in terms of possible locations of Cu2+ ions in the microporous zeotypic OMS-2 structure.
Journal ArticleDOI
Copper entrapment and immobilization during cement hydration in concrete mixtures containing copper tailings
Felipe Vargas,Felipe Vargas,Marco A. Alsina,Marco A. Alsina,Jean François Gaillard,Pablo A. Pastén,Mauricio Lopez +6 more
TL;DR: In this paper, the mechanisms by which copper is entrapped in the cementitious matrix were investigated, by combining microscopic and spectroscopic approaches, and it was shown that decreasing the water-to-binder ratio was statistically relevant to reduce copper leaching.
Journal ArticleDOI
Chemical Sensitivity of Valence-to-Core X-ray Emission Spectroscopy Due to the Ligand and the Oxidation State: A Computational Study on Cu-SSZ-13 with Multiple H2O and NH3 Adsorption
TL;DR: In this paper, the authors compared vtc-XES spectra of H2O and NH3 adsorbed on Cu+ (or Cu2+) cations, and found a blue shift for the kβ″ lines from a Cu-O to a Cu−N ligand.
Journal ArticleDOI
Comparing CuAPO-5 with Cu:ZSM-5 in the selective catalytic reduction of NOx : An in situ study
Karina Mathisen,David G. Nicholson,Andrew M. Beale,Manuel Sanchez-Sanchez,Gopinathan Sankar,W. Bras,Serge Nikitenko +6 more
TL;DR: In this article, the X-ray absorption spectroscopy (XAS) was used to follow changes in the valence state and the local environment of copper as the different materials reacted with the individual components of this particular deNOx process.
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