Spectroscopic and photophysical properties of some new rhodamine derivatives in cationic, anionic and neutral micelles

The spectroscopic and photophysical characterization of rhodamine 123 (dye 1), 4,5-dibromorhodamine methyl ester (dye 2) and 4,5-dibromorhodamine n-butyl ester (dye 3) are reported in homogeneous media like water and some alcohols and also in microheterogeneous media; anionic sodium dodecylsulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB) and neutral triton X-100 (TX) micelles. The selective biodistribution of these ionic drugs in tissues and membranes strongly influence their photosensitizing properties which have been part of our earlier studies, Results suggest that the hydrogen bonding capability of the amino end group lone pair of these dyes dominates in water. All these dyes interact with anionic SDS micelles, The interaction is mainly electrostatic in nature. At low SDS concentrations (below c.m.c,), dye-SDS aggregate formation takes place, But above c.m.c, only the monomeric dye form is observed. The penetration of dye 3 in SDS is a little less compared to dyes 1 and 2, Dyes 2 and 3 show a finite interaction with CTAB micelle unlike dye 1, With neutral TX micelles all the dyes form strong complexes. The fluorescence quantum yield (Phi(F)) of these three dyes in TX is lower. In time-resolved fluorescence experiments, two lifetimes are observed. The effects of the TX concentration on the fluorescence decay are measured. The decay associated spectra of dye 2 in TX are obtained by global compartmental analysis, The dye-surfactant interaction mechanisms are also discussed.