Electron exchange complexes

Similar films are obtained from powdered molecular sieves loaded with organic molecules Zeolite Y microparticles embedded into a polystyrene film and loaded with appropriately sized transition metal complexes allow selective electron exchange reactions between trapped and mobile species in the film... 

Intervalence Charge Transfer Emd Electron Exchange Studies of Dinuclear Ruthenium Complexes Robert J. Crutchley... 

Pishko MV, Katakis I, Lindquist SE, Ye L, Gregg BA, Heller A. 1990. Direct electron exchange between graphite electrodes and an adsorbed complex of glucose oxidase and an osmium-containing redox polymer. Angew Chem 102 109-111. 

Azo-bridged ferrocene oligomers also show a marked dependence on the redox potentials and IT-band characteristics of the solvent, as is usual for class II mixed valence complexes 21,22). As for the conjugated ferrocene dimers, 2 and 241 the effects of solvents on the electron-exchange rates were analyzed on the basis of the Marcus-Hush theory, in which the t/max of the IT band depends on (l/Dop — 1 /Ds), where Dop and Ds are the solvent s optical and static dielectric constants, respectively (155-157). However, a detailed analysis of the solvent effect on z/max of the IT band of the azo-bridged ferrocene oligomers, 252,64+, and 642+, indicates that the i/max shift is dependent not only on the parameters in the Marcus-Hush theory but also on the nature of the solvent as donor or acceptor (92). 

Because of the presence of many polypyridine ligands, each capable of undergoing several reduction processes [38], the electrochemical reduction of this type of dendritic compound produces very complex electron exchange patterns. 

In contrast to the dipole-dipole interaction, the electron-exchange interaction is short ranged its rate decreases exponentially with the donor-acceptor distance (Dexter, 1953). This is expected since, for the electron exchange between D and A, respective orbital overlap would be needed. If the energy transfer is envisaged via an intermediate collision complex or an exciplex, D + A—(D-------A)- D + A, then Wigner s rule applies there must be a spin com-... 

The low-spin t g [Ru(H20)6]3+ is four orders of magnitude more labile than the t g [Ru(H20)6]2+ and exchanges water by an Ia mechanism (125). The slow water exchange on both complexes allowed the direct measurement of the electron exchange of the [Ru(H20)e]3+/2+ couple in acidic solution (Eq. (10)) (133). 

This is also valid for the more complex spinel solid solutions of FejO, Mn304 and CO3O4, in which electron exchange occurs in addition to substitutional disorder (2). 

A recently proposed semiclassical model, in which an electronic transmission coefficient and a nuclear tunneling factor are introduced as corrections to the classical activated-complex expression, is described. The nuclear tunneling corrections are shown to be important only at low temperatures or when the electron transfer is very exothermic. By contrast, corrections for nonadiabaticity may be significant for most outer-sphere reactions of metal complexes. The rate constants for the Fe(H20)6 +-Fe(H20)6 +> Ru(NH3)62+-Ru(NH3)63+ and Ru(bpy)32+-Ru(bpy)33+ electron exchange reactions predicted by the semiclassical model are in very good agreement with the observed values. The implications of the model for optically-induced electron transfer in mixed-valence systems are noted. 

A quantitative determination of such matrix elements (to be elaborated below) is of crucial importance because it not only allows an absolute evaluation of the desired rate constants but also helps to reveal the qualitative aspects of the mechanism. In particular, questions regarding the magnitude of electronic transmission factors and the relative importance of ligands and metal ions in facilitating electron exchange between transition metal complexes can be assessed from a knowledge of... 

The low-spin t2g [Ru(H20)6] is by four orders of magnitude less labile than the t2g [Ru(H20)6] " (83). An la mechanism was attributed from the negative AV. Because the water exchange on both ruthenium complexes is slow, electron exchange could be measured directly by NMR on the [Ru(H20)6] " couple (27). It has been shown that the self-exchange on the... 

The hexacyanoferrate(II)/(III) electron exchange reaction is strongly catalyzed by cations such as K" ". However if the K" " is complexed by, e.g., 18-crown-6 or the cryptand [2.2.2] then the rate constant for the uncatalyzed reaction can be determined. Carbon-13 NMR spectroscopy has established that is 240 s (at 298 K), with AVyyJ = —11.3 cm mol Pressure effects on... 

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