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Abstract:
Most chemical reactions are carried out in solutions and those encountered
between charged particles are known to be influenced by electrostatic
interaction between them. Electrostatic interactions are important for the
selforganization of synthetic supramolecular systems and for the function of
biomacromolecules such as DNA and proteins. The theory of such interactions is
usually based on Coulomb’s law, thus considering the space between the ions as
a dielectric continuum. At short distances between ions this is unlikely to be
a good approximation – it may be necessary to include salvation explicitly in
the model. The theoretical calculation of the electrostatic interaction is
still difficult because many factors have to be taken into account. These are
the spatial distribution of the charge over the reagents (in nonspheric
particles), the possibility of the association of reagents with a counterion
and reliable data on the microscopic dielectric constant of the medium in the
vicinity of ions, etc. [5] As to the experimental research on the role of
electrostatic interaction in ionic reactions, the most complicated thing is
that the reaction rate depends on a great number of factors each of which is
difficult to estimate a priori. The spin exchange between charged particles is
influenced by a much smaller number of factors. The study of spin exchange is
therefore a convenient method to investigate the influence of electrostatic
interactions on the efficiency of various processes in liquids. In our short
time work, we use this method to probe the electrostatic interactions in
solutions and try to obtain some useful information on the properties by
varying the solution components.
Firstly in the theoretical part we will give a short introduction of the
background of the electrostatic interaction in solutions and the principle of
EPR, secondly in the experimental part we will study the various factors
influencing the electrostatic interactions by varying the solvent/solvent
mixtures for the oppositely charged spin probes, Cat1 and Fs, via EPR
spectroscopy to quantify exchange interaction. In the discussion part, we
consider whether the experimental results can be explained by simple theories
on electrostatic interaction and exchange coupling in solution.
