Unusual distance dependences of electron transfer rates

Abstract

Usually the rates for electron transfer (kET) decrease with increasing donor-acceptor distance, but Marcus theory predicts a regime in which kET is expected to increase when the transfer distance gets longer. Until recently, experimental evidence for such counter-intuitive behavior had been very limited, and consequently this effect is much less well-known than the Gaussian free energy dependence of electron transfer rates leading to the so-called inverted driving-force effect. This article presents the theoretical concepts that lead to the prediction of electron transfer rate maxima at large donor-acceptor distances, and it discusses conditions that are expected to favor experimental observations of such behavior. It continues with a consideration of specific recent examples in which electron transfer rates were observed to increase with increasing donor-acceptor distance, and it closes with a discussion of the importance of this effect in the context of light-to-chemical energy conversion.

Shortcuts for Electron‐Transfer through the Secondary Structure of Helical Oligo‐1,2‐Naphthylenes

“…1.1 eV (Table ), in line with numerous previously investigated systems, including many ET enzymes . A λ value of 1.1 eV is furthermore compatible with a simple model, which treats the donor and the acceptor as two charged spheres (with radii of 4 Å) interacting with each other in electrostatic fashion through CH 3 CN (with a dielectric constant of 35.7 and a refractive index of 1.3441) . Thus, there is no unusual behavior of λ in our dyads.…”

“…[14c] A l value of 1.1 eV is furthermore compatible with a simple model, [15a] which treats the donor and the acceptora s two charged spheres (with radii of 4 )i nteracting with each other in electrostatic fashion through CH 3 CN (with ad ielectric constant of 35.7 and ar efractive index of 1.3441). [22] Thus, there is no unusual behavior of l in our dyads. The striking finding is that H DA is nearly insensitive to bridge elongation and even slightly increases from 1.5 AE 0.1 cm À1 to 2.1 AE 0.1 cm À1 between W1 and W3 (Table 1).…”

Tuning the Intrinsic Properties of Carbon Nitride for High Quantum Yield Photocatalytic Hydrogen Production

“…This rate of electron tunneling decays exponentially with distance and, therefore, nullifies the chance of electron–hole recombination. This could occur with a spatial separation of only a couple of nanometers . Each forward electron transfer will then be several orders of magnitude faster than the competing recombination pathways to ground.…”

N10‐carbonyl‐substituted phenothiazines inhibiting lipid peroxidation and associated nitric oxide consumption powerfully protect brain tissue against oxidative stress

“…Several studies report, for example, the phenothiazine blockade of •OH as produced by 6-aminodopamine in a xanthine oxidase xanthine experimental system (Heikkila, Cohen, & Manian, 1975) and also with the Fenton reaction (Borges et al, 2010). Phenothiazines are lipophilic and partition preferentially into membranes; as electron transfer can occur over some distance, interception of •OH may not be impossible (Kuss-Petermann & Wenger, 2016). Of course, administered drugs do not approach the concentration of bulk membrane and the formation of lipid peroxyl radicals from •OH may be the dominant pathway in vivo.…”