Carbon redox properties

The redox properties of a series of heterometal clusters were assessed by electrochemical and FPR measurements. The redox potentials of derivatives formed in D. gigas Fdll were measured by direct square wave voltammetry promoted by Mg(II) at a vitreous carbon electrode, and the following values were determined 495, 420,... 

Diener MD, Bolskar RD, Alford JM (2002) Redox properties and purification of endohedral metallofullerenes. In Akasaka T, Nagase S (eds.) Endofullerenes a new family of carbon clusters. Kluwer, Dordrecht, pp. 133-151. 

Use of the tripodal ligand Saltren creates a tetranuclear complex [Mn402(Sal-tren)2][MnCl4] 2CH3CN (172) having a fused open cubane structure without a carboxylate group. At 300 K the value of the effective magnetic moment for (172) is 5.1 /Ub, which decreases to 2.0 /iB at 4.2 K. The redox properties of (172) in propylene carbonate have been studied by cyclic voltammetry. Two oxidation responses are observed at = —0.32V and 0.43 V vs. SCE. 

H2 and CO, whereas part of the ethoxy species generated on the supports is further oxidized to acetate species, which decomposes to CH4 and/or oxidizes to CO2 via carbonate species [202]. Hence supports with redox properties that help the oxidation of ethoxy species and metals with a high capacity to break C-C bonds and to activate C-H bonds are suitable for use in catalysts applied to the partial oxidation of ethanol. 

In order to improve the resistance of Ni/Al203-based catalysts to sintering and coke formation, some workers have proposed the use of cerium compounds [36]. Ceria, a stable fluorite-type oxide, has been studied for various reactions due to its redox properties [37]. Zhu and Flytzani-Stephanopoulos [38] studied Ni/ceria catalysts for the POX of methane, finding that the presence of ceria, coupled with a high nickel dispersion, allows more stability and resistance to coke deposition. The synergistic effect of the highly dispersed nickel/ceria system is attributed to the facile transfer of oxygen from ceria to the nickel interface with oxidation of any carbon species produced from methane dissociation on nickel. 

Due to the large number of metals that can form TNT EMFs and the usually wide cage-size distribution obtained in each case, the number of different compounds that have been described and studied by electrochemistry is quite large. All of these new fascinating compounds usually show very rich redox properties and therefore have been considered promising candidates for molecular electronic applications, such as photovoltaics. The redox behavior of these compounds is influenced by the size and symmetry of the carbon cage and the nature of the metal. 

The oxidation of guanine (G) and adenine (A) follows a two-step mechanism involving the total loss of four electrons and four protons showing current peaks at approximately 0.9 and 1.2 V, respectively. However, the redox properties are dependent on the pH, the ionic strength of the electrolyte, and the electrode material.2 The reader is referred to a recent review by Palecek and coworkers for a more comprehensive discussion regarding the electrochemical mechanism of the oxidation and reduction of DNA bases on carbon and mercury electrodes.3 4 Guanine oxidation is irreversible and occurs in two consecutive steps (Fig 10.1).5... 

Metallic nanoparticles and single-walled carbon nanotubes (SWCNTs) exhibit nanoscale dimensions comparable with the dimensions of redox proteins. This enables the construction of NP-enzyme or SWCNT-enzyme hybrids that combine the unique conductivity features of the nanoelements with the biocatalytic redox properties of the enzymes, to yield wired bioelectrocatalyts with large electrode surface areas. Indeed, substantial advances in nanobiotechnology were achieved by the integration of redox enzymes with nanoelements and the use of the hybrid systems in different bioelectronic devices.35... 

Ferrocene is composed of a pair of 6-7r-electron carbon arrays and a 6-d-electron iron(II) atom. Ferrocene-fullerene donor-acceptor dyads carry all the requisites for electron-transfer phenomena. However, data for the formation of ferrocene-fullerene hybrids are not abundant. Some such dyads have already been synthesized following the methodology of 1,3-dipolar cycloaddition of the appropriate azome-thine ylides to C60, with either variable-spacing building blocks or a rigid-bridge all-cj-bonded framework, in order to tune the redox properties of the system [40,234, 248-251]. Another novel dyad that contained two covalently bound ferrocene units was recently synthesized via cyclopropanation of the fullerene core [252]. 

The mechanism of melatonin s interaction with reactive species probably involves donation of an electron to form the melatoninyl cation radical or through a radical addition at the site C3. Other possibilities include hydrogen donation from the nitrogen atom or substitution at position C2, C4, and C7 and nitrosation [169]. The mechanisms by which melatonin protects against LP most likely involve direct or indirect antioxidant and free-radical scavenging activities of this indoleamine [169,171]. 2-Phenyl indole derivatives have redox properties because of the presence of an electron-rich aromatic ring system that allows the indoleamine to easily function as an electron donor. For these derivatives, the possible antioxidant mechanism might be most probably toward carbon-centered radicals described by Antosiewicz et al. [172]. 

Mineralization (meaning a complete oxidation) of numerous organic species cannot be regarded only as an oxidation process. In many cases oxidation must be preceded by reduction steps, eg photocatalyzed transformation of CC14 to C02 and Cl requires first reduction of carbon(IV) to lower oxidation states, followed by its reoxidation to C02 [30], In this context redox properties of an excited semiconductor play a crucial role. Photogenerated holes should support highly oxidative potential, but at the other surface sites an efficient reducer (electron) should also be available [64,65],... 

In dehalogenating enzymes of anaerobic microorganisms, corrinoid cofactors have a newly discovered further role in the redox catalysis of the energy conserving dehalogenation of chloro(hydro)carbon compounds ( dehalorespiration ), and the specific redox properties of the protein-bound unusual corrinoids are of particular current interest. 

Therefore, the co-ordinating properties (intrinsic Lewis acidity) and the redox properties (electron transfer) of the metal ion are important for the first step, and for the transformation of the adsorbed hydrocarbon into the nitrile rather than to carbon oxides and HCN. It is also worth noting that when a conventional alkene ammoxidation catalyst is used, such as Bi/Mo/O, the performance is much worse (yield 4.5% at 450°C). 

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