Organic redox centers

Eoxi 0.54 V versus Ag/AgCI Eox2 0.55 V versus Ag/AgCI AEox = 0.01 V Scan rate 43 mV s-  

Potentials versus Fc+/Fc (estimated for 6 by subtracting 0.53 V from values reported against SCE) 

MeCN + 0.1 M BU4NCI04for6 CH2CI2 + O.I M BU4NPF6for7-9,11,12 MeCN + 0.1 M Et4NCI04for 10 

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Dinolfo PH, Coropceanu V, Bredas J-L, Hupp JT (2006) A new class of mixed-valence systems with orbitally degenerate organic redox centers examples based on hexa-rhenium molecular prisms. J Am Chem Soc 128 12592-12593... 

Figure 5 Proline-bridged donor-acceptor complexes with organic redox centers.

The energy necessary to generate ATP is extracted from the oxidation of NADH and FADH2 by the electron transport chain, a series of four protein complexes, denoted Complexes I-IV (Fig. 7b). NADH is oxidized by Complex I FADH2 is oxidized by Complex II. Each complex contains multiple redox centers several iron-sulfur proteins and flavin mononucleotide in Complex I, and three iron-sulfur centers and a heme in Complex II. The electrons are then passed to coenzyme Q, which contains an organic redox center. Coenzyme Q transfers the electrons to Complex III. Complex III contains three hemes and... 

Although the broad rate/-AG°et dependences exhibited by the quinone-mediated electron transfers are suggestive of the coupling of high frequency, internal cofactor modes [8,13], and calculated FC factors for organic redox centers indicate a possib e contribution of 0.1-0.3 eV to X [28,29], our results demonstrate that if there are distinct contributions from internal modes of the cofactors to X, they are not sufficiently different to cause a measurable effect on the rateZ-AG et profile. This suggests that small-molecule redox centers include a set of modes with a comparable distribution of frequencies that can be coupled to the reaction. This is consistent with the general... 

The field of modified electrodes spans a wide area of novel and promising research. The work dted in this article covers fundamental experimental aspects of electrochemistry such as the rate of electron transfer reactions and charge propagation within threedimensional arrays of redox centers and the distances over which electrons can be transferred in outer sphere redox reactions. Questions of polymer chemistry such as the study of permeability of membranes and the diffusion of ions and neutrals in solvent swollen polymers are accessible by new experimental techniques. There is hope of new solutions of macroscopic as well as microscopic electrochemical phenomena the selective and kinetically facile production of substances at square meters of modified electrodes and the detection of trace levels of substances in wastes or in biological material. Technical applications of electronic devices based on molecular chemistry, even those that mimic biological systems of impulse transmission appear feasible and the construction of organic polymer batteries and color displays is close to industrial use. 

Our strategy is to incorporate a prolate redox molecule into the hydrocarbon phase of the organized monolayer. Steric restraints imposed by a dose-packed monolayer would presumably force the redox molecule to adopt an orientation parallel to the hydrocarbon tails. Spacing can then be controlled by a short hydrocarbon chain between the redox center and the metal. A class of molecules fitting these requirements are the assymetric 4,4 -bipyridiniums ... 

Metalloenzymes or metal ion-activated enzymes catalyze an enormous variety of organic reactions that are not restricted to any particular reaction class, but appear as catalysts for all types of reactions. Thus neither the presence of the metal ion nor the reaction type seems to be restrictive as far as metal-assisted enzyme catalysis is concerned. In some cases the metal ion appears to function as an electron acceptor or donor, but flavin cofactors have substituted as redox centers during evolution in some enzymes. 

We have shown how the band structure of photoexcited semiconductor particles makes them effective oxidation catalysts. Because of the heterogeneous nature of the photoactivation, selective chemistry can ensue from preferential adsorption, from directed reactivity between adsorbed reactive intermediates, and from the restriction of ECE processes to one electron routes. The extension of these experiments to catalyze chemical reductions and to address heterogeneous redox reactions of biologically important molecules should be straightforward. In fact, the use of surface-modified powders coated with chiral polymers has recently been reputed to cause asymmetric induction at prochiral redox centers. As more semiconductor powders become routinely available, the importance of these photocatalysts to organic chemistry is bound to increase. 

In 2006, for the first time, the decoration of viral particles with redox-active moieties was reported [83,96]. The decoration of CPMV with a redox-active organo-metallic complex, ferrocene, and also with an organic redox-active compound, viologen, was achieved. Both approaches led to the generation of monodisperse redox-active nanoparticles the redox centers were presented in multiple copies on the solvent-exposed outer surface. 

Whereas the electron acceptors in the anaerobic organisms are the bacterial-type ferredoxins that contain [4Fe-S] clusters as the redox center, in the case of the halobacteria the electrons are transferred to [2Fe-S] ferredoxins. These ferredoxins were isolated from two different halobacteria and their amino acid sequences were determined (Hase et al., 1977, 1980) and shown to be highly homologous to the chloroplast (and cyanobacterial) ferredoxins. The implications of these perplexing findings for the question of the molecular evolution of the system is discussed in detail in Kerscher and Oesterhelt (1982). 

The organometallic ferrocene moiety is an attractive redox center to integrate into macrocyclic polyether ligands because, apart from its established functional group organic chemistry, ferrocene itself is elec-trochemically well behaved in most common solvents undergoing a reversible one-electron oxidation (43). 

The electrochemical properties of (40)-(47) in the presence and absence of stoichiometric amounts of Na+ and K+ guest cations were investigated in acetonitile solution by cyclic voltammetry. Table VI shows that addition of alkali metal salt in 1 1 molar ratio produces anodic shifts (AE) in the original redox couple of 40-320 mV in the reduction potentials of the respective host s molybdenum redox center. Comparing (45)-(47) with the organic redox-active quinone systems described earlier (see Table I), in the case of Na+ guest cation these AE... 

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