Solvent reorganization of electron transitions in viscous solvents

Pradip K. Ghorai, Dmitry V. Matyushov

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

We develop a model of electron transfer reactions at conditions of nonergodicity when the time of solvent relaxation crosses the observation time window set up by the reaction rate. Solvent reorganization energy of intramolecular electron transfer in a charge-transfer molecule dissolved in water and acetonitrile is studied by molecular dynamics simulations at varying temperatures. We observe a sharp decrease of the reorganization energy at a temperature identified as the temperature of structural arrest due to cage effect, as discussed by the mode-coupling theory. This temperature also marks the onset of the enhancement of translational diffusion relative to rotational relaxation signaling the breakdown of the Stokes-Einstein relation. The change in the reorganization energy at the transition temperature reflects the dynamical arrest of the slow, collective relaxation of the solvent related to the relaxation of the solvent dipolar polarization. An analytical theory proposed to describe this effect agrees well with both the simulations and experimental Stokes shift data. The theory is applied to the analysis of charge-transfer kinetics in a low-temperature glass former. We show that the reorganization energy is substantially lower than its equilibrium value for the low-temperature portion of the data. The theory predicts the possibility of discontinuous changes in the dependence of the electron transfer rate on the free energy gap when the reaction switches between ergodic and nonergodic regimes.

Original languageEnglish (US)
Article number144510
JournalJournal of Chemical Physics
Volume124
Issue number14
DOIs
StatePublished - Apr 14 2006

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electron transitions
Electron transitions
electron transfer
charge transfer
Temperature
cross relaxation
temperature
energy
Electrons
Charge transfer
coupled modes
acetonitrile
reaction kinetics
switches
simulation
breakdown
transition temperature
free energy
molecular dynamics
Free energy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Solvent reorganization of electron transitions in viscous solvents. / Ghorai, Pradip K.; Matyushov, Dmitry V.

In: Journal of Chemical Physics, Vol. 124, No. 14, 144510, 14.04.2006.

Research output: Contribution to journalArticle

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