PHOTOPHYSICAL PROPERTIES OF (DIMETHYLAMINO)ANTHRAQUINONES - RADIATIONLESS TRANSITIONS IN SOLVENT AND POLYELECTROLYTE MEDIA

Substitution of 9,10-anthraquinone with dialkylamino groups in the 2(6 ) positions results in either highly solvent-sensitive fluorescence em ission from an intramolecular charge transfer state or, for a symmetri cal substitution pattern, an intensely absorbing triplet transient. Fo r the 2-dimethylamino derivative 1, the fluorescence quantum yield is strongly dependent on solvent polarity, consistent with the imposition of a nonradiative decay channel involving motion of the amine moiety that is favored in more polar media. The emission yield is uniformly l ow for the symmetrical bis-substituted derivative 2 due to a competiti ve intersystem crossing which yields strongly absorbing triplet transi ents that decay in the microsecond regime. The binding of dyes to poly (methacrylic acid) (PMAA) is particularly efficient for the polyelectr olyte in its globular or ''hypercoiled'' conformation in water (acid f orm, pH 3.0). For bound dye the yield of fluorescence for 1 is increas ed significantly; the triplet states for 2 are especially long-lived a nd resist excited-state quenching.