Limiting fluorescence anisotropies of perylene and xanthene derivatives

Abstract

The limiting fluorescence anisotropies (r₀) of perylene, perylenyl, perylenoyl and xanthene derivatives in different solvents, micelles and lipid vesicles have been determined. It is found that r₀= 0.369 ± 0.002 for the perylene and the perylenyl compounds, r₀= 0.377 ± 0.002 for the perylenoyl compounds and r₀= 0.373 ± 0.002 for the xanthene derivatives. Among the xanthenes, fluorescein monoglucoronide (FG) is an exception with r₀= 0.392. It appears, however, that the absorption and fluorescence spectra of FG also differ markedly in shape from those of fluorescein and different rhodamines. The reason for r₀ < ⅖ is not compatible with Jablonski′s theory of torsional vibrations of a rigid molecule, or a free rotational motion in the solvent cavity, but seems to be an inherent property of the chromophoric part of a molecule.