Proton-couple electron-transfer reactions

From the ab initio quantum chemistry coupled with a molecular dynamics treatment of the surrounding media, Zhao and Cuckier have reported a study of a proton coupled electron transfer reaction [115],... 

Zhao, X. G. and Cuckier, R. I. Molecular dynamics and quantum chemistry study of a proton-coupled electron transfer reaction, J.Phys.Chem., 99 (1995), 945-954... 

For aminophenols, one-electron oxidation and the proton elimination can run together in one stage. This leads to a cation-radical containing O and +NH3 fragments within one and the same molecular carcass (Rhile et al. 2006). Such concerted reactions are classified as proton-coupled electron transfer (Mayer 2004). Proton-coupled electron transfer differs from conventional one-electron redox reaction in the sense that proton motion affects electron transfer. Because the transfers of a proton and an electron proceed in a single step, we can say about the hydrogen-atom transference, (H+ -I- e)=H. It is the fundamental feature of proton-coupled electron-transfer reactions that the proton and electron are transferred simultaneously, but from different places (see Tanko 2006). 

Shafirovich V, Geacintov NE (2004) Proton-Coupled Electron Transfer Reactions at a Distance in DNA Duplexes. 237 129-157... 

Proton-Coupled Electron Transfer Reactions at a Distance in DNA Duplexes... 

Cho S-l, Shin S (2000) Comment on the mechanism of proton-coupled electron transfer reactions. J Mol Struct (Theochem) 499 1-12... 

Effect of Pressure on Proton-Coupled Electron Transfer Reactions of Seven-Coordinate Iron Complexes in Aqueous Solution It has been shown that seven-coordinate Fe(III) diaqua complexes consisting of a pentaaza macrocyclic ligand possess superoxide dismutase (SOD) activity, and therefore could serve an imitative SOD function.360 Choosing appropriate chemical composition of a chelate system yielded suitable pKa values for the two coordinated water molecules so that the Fe(III) complexes of 2,6-diacetylpyridine-bis(semicarbazone) (dapsox) and 2,6-diacetylpyridine-bis(semioxamazide) (dapsc) (see Scheme 7.12) would be present principally in the highly active aqua-hydroxo form in solution at physiological pH.361... 

Hammes-Schiffer S. Theoretical perspectives on proton-coupled electron transfer reactions. Acc. Chem. Res. 2001, 34, 273-281. 

Quinones represent an important class of compound that undergo proton-coupled electron transfer reactions [35]. The order and kinetics of the two-electron/two-proton redox reactions of the quinone (Q)/hydroquinone (H2Q) couple continue to be active subjects of investigation. The interconversion of Q to H2Q can involve up to seven different intermediates depending on the pH of the solution and the solvent. However, in low-pH electrolytes electrochemically reversible behavior can be observed despite the significant changes that accompany redox switching. Beyond... 

Okamura, M. Y., and Feher, G., 1995, Proton-coupled electron transfer reactions of Qg in reaction centers from purple bacteria. In Anoxygenic Photosynthetic Bacteria, (R. E. Blankenship, M. T. Madigan, and C. E. Bauer, eds.) pp. 5779594, Kluwer Academic Publishers, DordrechL The Netherlands. 

Hammes-Schiffer S. Theoretical perspectives on proton-coupled electron transfer reactions. Acc. Chem. Res. 2001 34 273-281. Khoshtariya DE, Wei J, Liu H, Yue H, Waldeck DH. Charge-transfer mechanism for cytochrome c adsorbed on nanometer thick films, distinguishing frictional control from conformational gating. J. Am. Chem. Soc. 2003 125 7704-7714. 

This Section addresses, in two sets of two chapters, two recent developments in proton transfer the ultrafast vibrational spectroscopic probing of the microscopic details of proton transfer in water and elsewhere, and the emergence of proton-coupled electron transfer reactions as a major reaction dass. 

Metal-oxo complexes abstract hydrogen atom from substrates faster than their protonated metal-hydroxo counterparts, as was shown for Mn(IV) compounds with crossed-bridged cyclam.136 Hydrogen atom abstraction is characterized by a fairly large H/D kinetic isotope effects KIE usually exceeds 3, and sometimes reaches values as high as 30 -0.58 In contrast, a modest kinetic isotope effect of about 1.3-1.5 is usually observed for proton-coupled electron transfer reactions.137,138... 

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