Reactivity and equilibriums in ionic micellar solution. Part 8. Models for specific counterion effects on the incorporation of charged amphiphilic substrates into like-charged ionic micelles

Abstract

Data for the quenching of the fluorescence of two anthracene-derived amphiphilic fluorescence probes (ethyldimethyl-(I) and trimethyl(3-(9-anthracenyl)propyl)ammonium bromide (II)) in aqueous micellar solutions of the quencher detergents N-hexadecylpyridinium chloride (HPCl), bromide (HPBr), and nitrate (HPNO/sub 3/) are analyzed in terms of a photophysical model which assumes static quenching of the micelle-incorporated probe and dynamic quenching of the residual fluorescence of the unincorporated probe by free detergent monomer and free counterions. This analysis provides values for the ground-state probe incorporation coefficient K/sub s/ which are compatible with independent estimates based on the quenching of the emission of the micelle-excluded Ru(bpy)/sub 3//sup 2 +/ ion by I under the same conditions. The results show that the incorporation coefficient is sensitive to the concentration of detergent and added salt present. 4 figures, 2 tables.