![]() ![]() This journal is © The Royal Society of Chemistry. Implications for solar fuel catalysis are discussed. at what driving force one or the other mechanism starts dominating. We thereby, for the first time, provide direct experimental evidence, that the vibronic coupling strength affects the switching point between CEPT and ETPT lim, i.e. Inverted region behavior, where the rate constant decreases as the reaction becomes more exoergic (i.e., as DeltaG(0) becomes more negative), has been observed. For cases when sufficiently strong oxidants are used, substitution of protons for deuterons leads to a switch from concerted electron-proton transfer (CEPT) to an electron transfer limited (ETPT lim) mechanism. The driving force dependence of the rate constants for nonadiabatic electron transfer (ET), proton transfer (PT), and proton-coupled electron transfer (PCET) reactions is examined. Sterically hindered pyridine bases gave larger reorganization energy for concerted PCET, resulting in a shift towards a step-wise electron first-mechanism in the zone diagrams. However, the exact nature of this process is still unclear. kET Aexp (Go + )2 4kT where the pre-exponential is. The light-induced proton transport in bacteriorhodopsin has been considered as a model for other light-induced proton pumps. Therefore, this expression is equivalent to the classical Marcus’ result for the electron transfer rate. Within this framework, we demonstrate strategies for mechanistic tuning, namely balancing of Δ G 0 ET and Δ G 0 PT, steric hindrance of the proton-transfer coordinate, and isotope substitution. For a thermally averaged rate it is proper to associate the average energy gap with the standard free energy of reaction, HA HD G0. These diagrams show the dominating mechanism as a function of driving force for electron and proton transfer (Δ G 0 ET and Δ G 0 PT) respectively. The mechanisms of proton-coupled electron transfers (PCETs), in which proton and electron transfers involve different molecular centers, is the object of active current attention in view of the role that such reactions play in many natural processes (1 3). Here, we apply mechanistic zone diagrams to illustrate the competition between concerted and stepwise PCET-mechanisms in the oxidation of 4-methoxyphenol by Ru(bpy) 3 3+-derivatives in the presence of substituted pyridine bases. of pH-dependent driving force, water appears as a remarkable proton acceptor in. However, determination and tuning of the PCET mechanism is often non-trivial. Proton-coupled electron transfers (PCET) are ubiquitous in natural and. The mechanism by which proton-coupled electron transfer (PCET) occurs is of fundamental importance and has great consequences for applications, e.g. ![]()
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