Rotational diffusion times for three mechanically similar phenoxazine dyes with differing electronic properties were measured. These studies probe the importance of dipole/dipole and ion/dipole couplings to the friction. The experimental results are compared with the predictions of available continuum theories of dielectric friction. Future directions for a more realistic model of dielectric friction are discussed.

Hydrogen-bonding self-assembly of multichromophore structure

Rotational diffusion studies on a pair of mechanically similar aminoanthraquinones with different electronic properties are used to explore solute/solvent interactions, specifically dielectric friction. In benzonitrile, the nonpolar solute (tetraaminoanthraquinone) exhibited a significantly longer rotation time than the polar analogue (diaminoanthraquinone), whereas in toluene the solutes had similar relaxation times. The experimental relaxation rates are compared with those predicted by both hydrodynamic and dielectric friction theories. A model recently developed model by Alavi and Waldeck ( J . Chem. Phys. 1991, 94, 6196) for calculating the dielectric friction shows a marked improvement over earlier approaches.

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