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The Dynamics of Preferential Solvation Department of Physical Chemistry, The Hebrew UniVersity, Jerusalem 91904, Israel

Summary: The Dynamics of Preferential Solvation
Noam Agmon
Department of Physical Chemistry, The Hebrew UniVersity, Jerusalem 91904, Israel
ReceiVed: March 13, 2002
A simple model describes the translational diffusion origin of preferential solvation. Assuming independent
polar ligands in the first solvation shell of the excited probe molecule, it presents an extension of the
Smoluchowski aggregation model to the reversible case. The model captures the main aspects of both
concentration and time dependence of spectral shifts obtained from steady-state and transient fluorescence
measurements. It provides a useful method for extracting the rate and equilibria coefficients for ligand exchange
in the first solvation shell of excited polar molecules.
1. Introduction
Molecules are stabilized by their interaction with the solvent,
and this induces a shift in their absorption or emission spectra
as compared with that in the gas phase.1 When a dipolar or
charged solute is introduced into a neat polar solvent, the solvent
responds predominantly by librational motions to optimize the
solute-solvent interactions. If the dipole is created (or enhanced)
by photoexcitation of a fluorescent probe molecule, the solvent
response manifests itself in a fast time-dependent Stokes shift
for the average fluorescence frequency, (t).2


Source: Agmon, Noam - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry