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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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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The Isotope Geochemistry of Zinc and Copper
TL;DR: Chaboy et al. as mentioned in this paper showed that the symmetry of the hexaaqua complex of Cu(H2O)62+ has a Jahn-Teller distortion effect (Sherman 2001; Bersuker 2006), whereby the two Cu-O distances of the vertical axial bond (Cu-Oax) are longer than four Cu O distances in the equatorial plane (Cu Oax).
Journal ArticleDOI
Unusual physical and chemical properties of Cu in Ce1-xCuxO2 oxides
Xianqin Wang,José A. Rodriguez,Jonathan C. Hanson,D. Gamarra,Arturo Martínez-Arias,Marcos Fernández-García +5 more
TL;DR: The structural and electronic properties of the Ce1-xCuxO2 nano systems were characterized with synchrotron-based X-ray diffraction, Xray absorption spectroscopy, and density functional calculations as mentioned in this paper.
Journal ArticleDOI
Methane Oxidation to Methanol Catalyzed by Cu-Oxo Clusters Stabilized in NU-1000 Metal-Organic Framework.
Takaaki Ikuno,Jian Zheng,Aleksei Vjunov,Maricruz Sanchez-Sanchez,Manuel A. Ortuño,Dale R. Pahls,John L. Fulton,Donald M. Camaioni,Zhanyong Li,Debmalya Ray,B. Layla Mehdi,Nigel D. Browning,Nigel D. Browning,Omar K. Farha,Omar K. Farha,Joseph T. Hupp,Christopher J. Cramer,Laura Gagliardi,Johannes A. Lercher,Johannes A. Lercher +19 more
TL;DR: Analysis of chemical reactivity, in situ X-ray absorption spectroscopy, and density functional theory calculations are used to determine structure/activity relations in the Cu-NU-1000 catalytic system.
Journal ArticleDOI
Methane to Methanol: Structure–Activity Relationships for Cu-CHA
Dimitrios K. Pappas,Elisa Borfecchia,Michael Dyballa,I. A. Pankin,Kirill A. Lomachenko,Andrea Martini,Matteo Signorile,Shewangizaw Teketel,Bjørnar Arstad,Gloria Berlier,Carlo Lamberti,Carlo Lamberti,Silvia Bordiga,Silvia Bordiga,Unni Olsbye,Karl Petter Lillerud,Stian Svelle,Pablo Beato +17 more
TL;DR: It is found that the CuII moieties responsible for the conversion are formed in the presence of O2 and that high temperature together with prolonged activation time increases the population of such active sites, and there is a linear correlation between the reducibility of the materials and their methanol productivity.
Journal ArticleDOI
Layered manganese oxides for water-oxidation: alkaline earth cations influence catalytic activity in a photosystem II-like fashion
TL;DR: In this paper, the synthesis of layered manganese oxides where they varied the interlayer cations, preparing a series of K-, Ca-, Sr- and Mg-containing birnessites were determined using X-ray absorption spectroscopy.
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