At copper

After rising at copper and zinc, the curve of metallic radii approaches those of the normal covalent radii and tetrahedral covalent radii (which themselves differ for arsenic, selenium, and bromine because of the difference in character of the bond orbitals, which approximate p orbitals for normal covalent bonds and sp3 orbitals for tetrahedral bonds). The bond orbitals for gallium are expected to be composed of 0.22 d orbital, one s orbital, and 2.22 p orbitals, and hence to be only slightly stronger than tetrahedral bonds, as is indicated by the fact that R(l) is smaller than the tetrahedral radius. 

However, consideration in terms of the ionic radius or the LFSE shows that both factors predict that the maximum stabilities will be associated with nickel(ii) complexes, as opposed to the observed maxima at copper(ii). Can we give a satisfactory explanation for this The data presented above involve Ki values and if we consider the case of 1,2-diaminoethane, these refer to the process in Eq. (8.13). 

Y2Ba4Cu7025 Nuclear quadrupole interaction at copper sites, EFG tensor at all sites is calculated using the point charge model, conclusion that holes in the Y2Ba4Cu70i5 lattice are localized predominantly at positions of chain oxygen... 

These reactions occur by oxidative addition at copper, followed by decomposition of the Cu(III) intermediate. 

Spectroscopic studies (XPS and HREELS) established first in 1980 that the activity of oxygen states in the oxidation of ammonia at copper-O surfaces was... 

In 1978, Wachs and Madix34 drew attention to the role of oxygen in the oxidation of methanol being not completely understood at copper surfaces. They established the role of methoxy species as the favoured route to the formation of formaldehyde and that to a lesser extent some methanol was... 

That chemisorbed oxygen was active in hydrogen abstraction, resulting in water desorption and the formation of chemisorbed sulfur, was first established by XPS at copper and lead surfaces.42 An STM study of the structural changes when a Cu(110)-O adlayer is exposed (30 L) to hydrogen sulfide at 290 K indicates the formation of c(2 x 2)S strings. 

Further evidence for surface effects upon the stereochemistry of electrochemical reduction of ketones comes from the discovery that the nature of the cathode material may effect stereochemistry. Reduction of 2-methylcyclo-hexanone affords pure trans-2-methylcyclohexanone at mercury or lead cathodes, a mixture of cis and trans alcohols (mostly trans) at nickel, and pure cis alcohol at copper 81 >. Reduction could not be effected at platinum presumably hydrogen evolution takes place before the potential necessary for reduction of the ketone can be reached. 

De Marco [285] evaluated three different types of copper (II) ion-selective electrodes. The copper sulfide electrode was found to be oxidised, whereas the copper selenide and copper sulfide electrodes were found to have chloride ion interference at copper (II) activities exceeding 10 8 M. 

The mechanisms of superoxide-dismuting activity of SODs are well established. Dismutation of superoxide occurs at copper, manganese, or iron centers of SOD isoenzymes CuZnSOD, MnSOD, or FeSOD. These isoenzymes were isolated from a variety of sources, including humans, animals, microbes, etc. In the case of CuZnSOD, dismutation process consists of two stages the one-electron transfer oxidation of superoxide by cupric form (Reaction (1)) and the one-electron reduction of superoxide by cuprous form (Reaction (2)). 

Figure 4. Left, copper TPD from a Ru(0001) surface at copper coverages corresponding to a, 0.6 ML, b, 1.5 ML, c, 2.5 ML, and d, 5.2 ML. (Data from ref. 3.) Right, electrochemical stripping curves as a function of Cu coverage (determined by AES) for vacuum deposited Cu on Ru(0001). (Data from ref. 16.)...

The oxidation of hydroxide ion in acetonitrile at copper, silver, gold, and glassy-carbon electrodes has been characterized by cyclic voltammetry. In the absence of bases the metal electrodes are oxidized to their respective cations (Cu+, Ag+, and Au+) at potentials that range from -0.2V vs. SCE for Cu to +1.3 V for Au. At glassy carbon OH is oxidized to 0 - (+0.35 V vs SCE) and then to... 

The oxidation of OH at copper, silver, and gold electrodes (Figures 1-3) also occurs at substantially less positive potentials than that at a glassy carbon electrode. This appears to be the result of coupling the unpaired electron of the -OH product with the s electron of metallic (atomic) copper, silver, or gold (d10s valence shell). ... 

Carbon Monoxide Reduction at Copper. At copper electrodes carbon monoxide is thought to be an intermediate in the reduction of carbon dioxide and is formed as the major product with nitric acid pretreated electrodes (2 and Kim, J. J. Summers, D. P. Frese, K. W., Jr. J. Electroanal. Chem. in press.). As the data in Table IV indicates, methane can be formed by carbon monoxide reduction at... 

Khader MM, Nasser SA, Hannout MM, El-Dessonki MS (1993) Photoelectrochemical dissociation of water at copper-doped p-GaAs electrodes. Int J Hydrogen Energy 18 921-924... 

Scheme 3 accounts for the various products formed, and it is consistent with known transformations in organometallic chemistry. In the first step, CO2 is reduced in a proton-coupled two-electron process to form adsorbed CO. That CO is an intermediate in the reduction of CO2 to hydrocarbons is supported by the following observations. (1) Reduction of CO at copper electrodes under the same conditions gives a similar distribution of hydrocarbon products. Reduction of formate, on the other hand, gave no hydrocarbon products [98, 102]. (2) CO on the electrode surface could be detected by cyclic voltammetry measurements. Fourier transform... 

The direct production of ethylene at copper electrodes is a striking example of a very complex multielectron reduction... 

The observation of currents attributable to the faradaic electrochemistry of nucleic acids was pioneered by Palecek and coworkers who studied DNA adsorbed on mercury or carbon electrodes [13]. The signals detected by Palecek were attributable to oxidation of the purines, which produced signals indicative of irreversible processes involving adsorbed bases. These reactions were used as a basis for electrochemical analysis of DNA. Kuhr and coworkers later showed that similar strategies could be developed for analysis of nucleic acids via oxidation of sugars at copper electrodes [14-16]. 

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