From dielectric relaxation to polar solvation dynamics in alcohols and amides

Abstract

Remarkable progress has been made in recent years in our understanding of the molecular dynamics of alcohols which has led to revision of much of our old ideas about these important chemical and biological solvents. In this article we present a molecular theory which not only provides a quantitative description of solvation dynamics in alcohols but also provides an insight into the complex dynamics of these liquids. The theory shows that the solvation dynamics in methanol is dominated by an ultra-fast component of time constant about 70 fs. Ethanol and propanol, on the other hand, do not sustain any such ultra-fast component of time constant of 70 fs or so; solvation, however, is much faster than what was believed previously. For all the liquids, the theoretical results are in almost complete agreement with the known experimental results. The theoretical studies also suggest that the experimental investigations of Joo <em>et al. [J. chem: Phys., </em>104 (1996) 6089] which report a much faster and larger ultrafast component in the same series of solvents, might have been more sensitive to non-polar part of solvation dynamics than the polar part.