On the Coherent Description of Diffusion‐Influenced Fluorescence Quenching Experiments II: Early Events

Abstract

In a previous article we showed how to perform and analyze steady-state and nanosecond time-resolved experiments on fluorescence quenching by electron transfer in a coherent manner. Now, by making use of a superior time resolution, we explore the first stages of this kind of reaction. The novel information gained enables us to merge the results on the viscosity and the driving-force dependencies of the reaction rate. A unique set of parameters for a single reaction channel suffices to describe all the results in the frame of differential encounter theory for diffusion-influenced, bimolecular, remote electron-transfer reactions. The inclusion of the solvent structure is crucial for the understanding of the reaction kinetics. To the authors' best knowledge, this is the first time that such a comprehensive set of data has been successfully and jointly explained in the field, with physically sound parameters for electron-transfer reactions.

Ultrafast Photochemistry in Liquids

“…By doing so, we can properly account not only for the mutual reactants' diffusion, but also for the specificities of the reaction itself, such as its distance and free-energy dependence. This approach has been successfully applied to irreversible photoinduced bimolecular ET (17,172,173), PT between photoacids and bases (111,174), and reversible bimolecular PT from photoacids to the solvent and subsequent geminate recombination of the proton/conjugate base pair (111,175). 7, the involvement of low-frequency skeletal deformations and the resulting ballistic wave-packet trajectory on the multidimensional potential energy surface were identified as rather general features of intramolecular PT for these types of molecules.…”

“…Isomerization processes that do not involve largeamplitude motions and bimolecular ET in strongly coupled donor-acceptor (DA) pairs can take place in less than 1 ps (9-13). Comparatively, dynamical processes related to the solvent, such as solvation dynamics, cooling, and diffusional transport, may take much longer, depending on solvent properties such as viscosity (14)(15)(16)(17). As there is no separation between the timescales of relaxation and reaction, the relaxation processes may influence or even control the outcome of the chemical reaction.…”

Bimolecular Photoinduced Electron Transfer in Imidazolium-Based Room-Temperature Ionic Liquids Is Not Faster than in Conventional Solvents

“…The variation of the relaxation time with the composition of the DMSO/GLY mixture is still a matter of research, but it has so far been successfully simulated with a single time. 32 This apparent independence of the τ L value cannot stem from possible differences in the composition of the DMSO/GLY mixture around the reactant pairs as this would also alter the reorientational dynamics of the solutes. However, even in the case of a multiphasic dielectric relaxation, which can be anticipated for DMSO/GLY, one can expect the fastest response to be dominated by DMSO and to have the most prominent impact.…”

Characterization of dimethylsulfoxide/glycerol mixtures: a binary solvent system for the study of “friction-dependent” chemical reactivity

“…in the study of the diffusion-influence in photo-induced electron transfer in the past. [24][25][26][27][28][29][30][31] In these papers, a reaction-diffusion model The data were thinned out by a factor of 5 for better visualization. The weighted residuals correspond to the best fits using the parameters given in Table 7.…”