Electron transfer coupling

E. Electron Transfer Coupled to a Change in Number of Ligands... 

Figure 6-5 shows an electrochemical cell of the redox reaction involving electron transfer coupled with a normal hydrogen electrode reaction. The cell diagram and cell reaction can be written, respectively, in Eqns. 6-13 and 6-14 ... 

The electrochemistry of dioxoosmium(VI) complexes has also been extensively studied. The tra 5-dioxoosmium(VI) complexes of polypyridyl and macrocyclic tertiary amine ligands display very similar proton-coupled electron transfer couples. In aqueous solutions at pH < 5-7 the cyclic voltammograms of n-a i-[0s (0)2(bpy)2] show a remarkable reversible three-electron couple and a one-electron Os coimle. In the Pourbaix diagram two break points are observed in the pH dependence of the Os couple, which correspond to the pAa values of Os —OH2 and Os —(OHXOH2) (Figure 10). The redox reactions are shown in Equations (41)-(43). At pH >8 the 3e Os wave splits into a pH-independent le Os wave and a 2e/2H" Os wave (Equations (44) and (45)). 

Among other electron-transfer coupling and substitution reactions may be mentioned the reduction of disulfides in the presence of Oz leading to sulfinic... 

H.-C. Chen and C.-P. Hsu, Ab initio characterization of electron transfer coupling in photoin-duced systems generalized Mulliken-Hush with configuration-interaction singles, J. Phys. Chem. A, 109 (2005) 11989-11995. 

Numerous concerted electron transfer/bond breaking or formation mechanisms have been suggested. We have already touched upon one (p. 84). the concerted electron transfer/coupling mechanism for EHD. If this mechanism is correct, it should have stereochemical consequences in a cyclic EHD process involving a conjugated system, such as that shown in eqn (108). A concerted step would be... 

Redox cycling of poly(thionine) films in aqueous acetic acid solution involves not only electron transfer (coupled with proton transfer to maintain electroneutrality), but also film solvation and acetic acid coordination... 

Electron transfer coupled with atom or proton transfer converts NO into lower oxidation state N ligands. The first example achieved with [M(S )] nitrosyl complexes is given by Eq. 29 (49, 71). 

Syrtsova, L. A. and Timofeeva, E. A. (2001) Electron transfer coupled with ATP hydrolysis in nitrogenase,... 

Syrtsova, L.A., Druzhinin, S.Yu., Uzenskaya, A.M., Khramov, A. V., Moravskii, A. P., and Likhtenshtein, G I. (1988), Kinetics of proton release in the process of nitrogenase electron transfer coupled with ATP hydrolysis, Biofizika 33, 31-5. 

Figure 6 The correlation, based on equation (61), of the absorption maxima of ion-pair charge transfer transitions to the difference in reduction potentials and the average of the reorganizational energies of the constiment electron-transfer couples. , Ru " with...

The ISC mechanism is not normally considered to be plausible. Both the RR and the RS mechanism may be further classified according to the sequence of microscopic steps (electron transfer, coupling, protonation and/or cyclization) and with reference to which of the steps is rate determining. For the RS mechanism, the second electron transfer may take place by a reaction in solution (as indicated in Scheme 2) or at the electrode if the coupling step is very fast. 

Andrieux, C.P, Hapiot, P, and Saveant, J.-M. 1984. Electron-transfer coupling of diffusional pathways Theory for potential step chronoamperometry and chronocoulometry. Journal of Electroanaytical Chemistry 1172, 49-65. 

According to Mitchell s chemiosmotic theory, photophosphorylation is driven by energy derived from electron transfer coupled to proton translocation. The results of postillumination discussed in the previous section further supports the notion that a proton gradient is the driving force for phosphorylation. It is therefore possible in principle that a similar proton gradient produced by artificial means might also be able to drive phosphorylation in a chloroplast membrane, entirely in the dark, i. e., without the aid of photo-induced electron transport. Such a scheme was indeed realized by the so-called acid-bath ATP-forma-tion demonstrated by Jagendorf and Uribe " in 1966. 

Great physiological significance can be attributed to the NADH oxidase of plasma membranes. These enzymes may indirectly contribute to oxygen activation by means of protein-bound iron reduction however, they are more important for transmembraneous electron transfer coupled to proton translocation and regulation of cell growth [22-24]. 

Molybdenum m) and Tungsten m). Reaction of [Mo(H20) ] with NO3 has been used to investigate the reduction of NO to NOJ by nitrate reductase. " The formation of [Mo204(H20)g] " and NOJ was observed spectrophotometrically and implies that the system involves the two electron transfer couple Mo VMo. A synthesis of MoCl3(THP)3 has appeared and its reactions with phosphines and reduction to Mo in a nitrogen atmosphere investigated. The equilibrium... 

UGHT INDUCED ELECTRON TRANSFER COUPLED TO HYDROGEN EVOLUTION... 

O-H deprotonation is coupled to C-C bond cleavage or a radical zwitterion is first formed which undergoes intramolecular electron transfer coupled to C—C bond cleavage. An oxyl radical intermediate is suggested for the base-catalysed decay of... 

Electron-transfer coupling across bridges of variable length increases as the separation of subcluster centroids decreases. The order of coupling is 41 S> 40e > 40b > 40a, 40c, and 40d. The effect becomes detectable at < 11 A and reaches a maximum at 7.5 A, or less if the bridge angle is overestimated. With reference to Fig. 28, it is seen that subcluster sepa-... 

The differences in relative activity of these compounds may be related to effects various constituents have on the ability to form highly reactive free radicals. A study which could help elucidate the actual mechanism of action of these compounds would be to examine (theoretically or experimentally) their ability to form radicals. If they express their herbicidal activity via this mechanism, then the energy and reactivity of free radical formation should show a positive correlation with the relative activity differences found in an intrinsic bioassay. For this purpose, the midpoint redox potential of the one-electron transfer couple DPE-NO2 DPE-N02 needs to be determined. This could be accomplished using such techniques as polarography or cyclic voltometry. It may also be feasible to study these reactions in darkness through the use of artificial electron... 

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