Abstract
The rotational diffusion of 9,10-disubstituted anthracenes is studied in various solvents. By systematic variation of the anthracene functionalities the influence of the electrostatic properties of the solute on the solute{endash}solvent frictional coupling is investigated. These studies explore the range of validity of continuum based dielectric friction models for describing the frictional coupling. It is found that a continuum model of the solvent with an extended charge distribution for the solute is adequate in unassociated solvents, but does not adequately describe the friction in the associated solvent, benzyl alcohol. {copyright} {ital 1997 American Institute of Physics.}