How do solvent relaxation dynamics affect electron transfer rates? A study in rigid solution

Abstract

Nonadiabatic electron transfer has been studied in glycerol in which the solvent relaxation time (rL) is varied (by temperature) from 10~s to 10'1 s. A strong dependence of rate on is observed with k « (tl)~°•6. A qualitative rationale suggests that the actual dependence for a nonadiabatic process can range from (rL)°t o (tl)-1 depending on whether the electronic coupling strength or solvent polarization determines the frequency factor for reaction. Such intermediate cases may be significant in a variety of condensed-phase electron-transfer processes.

Electron transfer reactions of rigid, cofacially compressed, π-stacked porphyrin–bridge–quinone systems

“…The extent to which solvent dynamics influence ET reactions depends on the nature of the solute-solvent interaction, which is electrostatic in origin. Since an intramolecular ET reaction is accompanied by a drastic change in molecular polarity, an ET reaction is more likely to be coupled to the motion of polar solvent molecules [265][266][267][268][269]. A theoretical treatment of this type of ET reaction is based on the Zusman's stochastic Liouville equation approach; following experimental verification, this mechanism has been termed as the solvent-controlled adiabatic reaction , respectively) models.…”

Electronic Coupling and Protein Dynamics in Biological Electron-Transfer Reactions

“…For example, showed A consequence of this analysis is that the same nuclear prefactor will not be appropriate for all protein systems. As noted by McGuire (18,19), the dependence of reaction rates on Tl will depend on the relative magni tudes of V(R) and Tl. Comparison of electron-transfer rates from different protein couples, or even different metal-heme derivatives of the same pro teins, must be made with caution.…”

“…It has been pointed out (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)) that, where the rate of solvent reorientation is slow relative to electron transfer, K* ^ vN = TL-X (2) where Tl is the longitudinal relaxation time of the solvent. The Franck- driving force).…”

“…The dependence of electron-transfer rates in condensed media on solvent relaxation and nonequilibrium solvation has been the subject of numerous studies workers (18,19) noted that, in the nonadiabatic limit, the frequency factor will be controlled not by solvent relaxation, but by electronic coupling, V(R), and thus be independent of TL:…”

Misleading aspects of the viscosity effect on the heterogeneous electron transfer reactions

“…Changing the temperature when keeping the solvent nature[18] is a promising approach, but there are a lot of complications for experimental electrochemistry 2. We are sure that the remark about the absence of any sucrose effects on the electrocapillary curves of mercury given in[20] results from experimental misunderstanding.…”