CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

CHAPTER 1
Introduction
1.1. Microsolvation
The process of solvation is a dynamical interaction of a solute with the solvent,
which leads to stabilization of the solute species in the solution. Studies on solvation of
charged and neutral chemical species (solutes) is one of the most important and attractive
area of research. If a chemical species (solute) is immersed into a solvent medium (bulk),
its charge distribution interacts with that of the solvent. Due to that the network of solvent
in the close proximity of the solute gets rearranged to allow the solute going through the
process of solvation. In the process of solvation, a few solvent molecules in the close
vicinity of the solute will interact instantaneously. Afterwards, more and more solvent
molecules from nearby surroundings will approach the solute and encapsulate the solute
to solvate it. The process of solvation involves different types of intermolecular
interactions, namely, ion-ion, ion-dipole, hydrogen bonding and dipole-dipole attractions
or van der Waals interactions. The nature of interactions depends on the nature of both
solute (neutral or ionic) and solvent (ionic, polar or nonpolar). When the process of
solvation of a solute in presence of large number of solvent molecules (i. e. in bulk) is
studied, the solvation model refers to macroscopic solvation model (continuum model)
(see Fig. 1). In this continuum model, rather than representing the charge distribution of
the solvent explicitly, it is replaced by a continuous electric field that represents a
1