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Molecular Rotation as a Tool for Exploring Specific Solute–Solvent Interactions
Author(s) -
Dutt G. B.
Publication year - 2005
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400337
Subject(s) - solvent , chemistry , hydrogen bond , chemical physics , relaxation (psychology) , solvent effects , molecular dynamics , molecule , solvent models , computational chemistry , thermodynamics , solvation , organic chemistry , physics , social psychology , psychology
Solute–solvent interactions play an important role in determining the physicochemical properties of liquids and solutions. As a consequence, understanding these interactions has been one of the long‐standing problems in physical chemistry. This Minireview describes our approach towards attaining this goal, which is to investigate rotational relaxation of a pair of closely related, medium‐sized nondipolar solutes in a set of appropriately chosen solvents. Our studies indicate that solute–solvent hydrogen bonding significantly hinders solute rotation. We have also examined the role of solvent size both in the absence and presence of specific interactions and it has been observed that the size of the solvent has a bearing on solute rotation especially in the absence of specific interactions. Our results point to the fact that only strong solute–solvent hydrogen bonds have the ability to impede the rotation of the solute molecule because, in such a scenario, hydrogen‐bonding dynamics and rotational dynamics transpire on comparable time scales. This aspect has been substantiated by measuring the reorientation times of the chosen solutes in solvents such as ethanol and trifluoroethanol, which have distinct hydrogen‐bond donating and accepting abilities, and correlating them with solute–solvent interaction strengths. As an alternative treatment, it has been shown that specific interactions between the solute and the solvent can be modeled as dielectric friction with the extended charge distribution model. This approach is not unrealistic considering the fact that specific as well as nonspecific interactions are electrostatic by nature and the differences between them are subtle.