Redox mediators organic metals

Redox proteins do not usually equilibrate with a platinum metal surface and, therefore, in order to establish thermodynamic equilibrium one must add a mixture of redox mediators to the solution. These are the same strongly coloured organic dyes... 

As starting materials for organic metals, organic substances must correspond to several general requirements. Namely, both acceptors and donors must form redox systems, with the participation of not only ion-radicals but also double-charged ions, A + e —> A + e — A or D e —> D+ e — Ion-radicals play a role as mediators in these two-electron transfers. Each one-electron... 

In the development of effective catalytic oxidation systems, there is a qualitative correlation between the desirability of the net or terminal oxidant, (OX in equation 1 and DO in equation 2) and the complexity of its chemistry and the difficulty of its use. The desirability of an oxidant is inversely proportional to its cost and directly proportional to the selectivity, rate, and stability of the associated oxidation reaction. The weight % of active oxygen, ease of deployment, and environmental friendliness of the oxidant are also key issues. Pertinent data for representative oxidants are summarized in Table I (4). The most desirable oxidant, in principle, but the one with the most complex chemistry, is O2. The radical chain or autoxidation chemistry inherent in 02-based organic oxidations, whether it is mediated by redox active transition metal ions, nonmetal species, metal oxide surfaces, or other species, is fascinatingly complex and represents nearly a field unto itself (7,75). Although initiation, termination, hydroperoxide breakdown, concentration dependent inhibition... 

Accelerants are used to increase coating weight and shorten coating time. Many different accelerants can be used including a variety of organic and transition metal compounds [60, 91], The predominant accelerant in commercial formulations is ferricyanide, Fe(CN)6 , which is added to acid chromate-fluoride formulations in concentrations ranging from 2 to 5 mM [92, 93]. The two primary theories for the action of Fe(CN)6 are (1) formation of mixed metal cyanide compounds [91, 94, 95] and (2) acceleration of the film-forming Cr(VI) to Cr(III) reduction reaction by Fe(CN)6 /" redox mediation [96]. These types of CCCs are discussed in more detail below. 

As shown by Eqs. 1 and 5, the ORRs in the aqueous alkaline electrolyte and in the non-aqueous electrolyte share the same two-electron reduction. This means that all catalysts showing the catalytic activity towards the ORR in alkaline fuel cells and metal-air batteries are theoretically suitable for the non-aqueous electrolyte Li-air batteries. Base on the chemical composition of the materials, these catalysts can be briefly classified into the following categories (1) porous carbon and doped carbon materials, (2) transition metal oxides, nitrides, and sulfides, (3) marcocyclic transition metal complexes, (4) non-precious metals and alloys, (5) precious metals and alloys, (6) organic redox mediators. 

The cyclobutadiene complex Ru6(/r6-C)(/r-CO)3(CO)i2( -C4Ph4) 138 is formed from redox-mediated ligand transfer between [Pd(acetone)2( 7 -C4Ph4)] and [Ru6(/r6-C)(CO)i6]. The metal core consists of a bond-opened octahedron, with the 77 -organic ligand bound to a basal ruthenium atom." ... 

Souto, R. M., L. Femandez-Merida, and S. Gonzalez, SECM imaging of interfacial processes in defective organic coatings applied on metallic substrates using oxygen as redox mediator. Electroanalysis, 21, 2009, 2640. 

Nitrate reductases (NaR) with an iron-sulfur center are used for nitrate conversion. Generally, nitrate is enzymatically reduced and NaR is in the oxidized form, which can be electrochemically reduced. However, the direct electron transfer between an enzyme and an electrode is strongly limited due to the fact that (1) the distance between the electrode surface and the redox active site of the enzyme, which is normally inside the globular protein, is large and (2) the orientation of donor to acceptor sites depends on the method of the immobilization of the enzyme at the electrode.Thus, low molar mass redox mediators including qui-nones, metal complexes, ferricyanide, derivatives of ferrocene, and organic redox dyes " have been used to facilitate the electron transfer between electrode and enzyme (Fig. 11.5). 

Synthetically useful organic reactions similar to ATRP, which are mediated by redox-active transition metal complexes, e.g., atom transfer radical addition or cyclization, can also be carried out successfully at low catalyst concentrations in the presence of both radical-based and non-radical (ascorbic acid) reducing agents. The continuous activator regeneration throughout the process via reduction has made these reactions more environmentally friendly than the traditionally used protocols. ... 

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