EFFECT OF SMALL CHEMICAL VARIATION AND FUNCTIONALITY ON THE SOLUBILIZATION BEHAVIOR AND RECOGNITION CAPABILITY OF 3H-INDOLES IN SDS AND CTAB

The solubilization behavior of five substituted derivatives of the mai n chromophore 2-phenyl-3,3-dimethyl-3H-indole has been studied in sodi um dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB) aq ueous micelles by fluorescence-decay lifetime measurements. These deri vatives are as follows: 2-((p-amino)phenyl)-3,3-dimethyl-3H-indole (I) , 2-((p-dimethylamino)phenyl)-3,3-dimethyl-3H-indole (II), amino)pheny l)-3,3-dimethyl-5-carboethoxy-3H-indole (III), amino)phenyl)-3,3-dimet hyl-5-carboethoxy-3H-indole (IV) and amino)phenyl)-3,3-dimethyl-5-carb oethoxy-3H-indole (V). Polarity- and viscosity-dependent fluorescence lifetimes and intensities of these molecular probes have been used to elucidate the micellar solubilization site. All molecular probes in CT AB and molecules I, II and V in SDS were found to occupy only one solu bilinization site, the intercalative binding in CTAB and the surface b inding in SDS. Molecules III and IV were shown to be able to recognize both sites in SDS. The data have been interpreted in terms of the fun ctionality effect of these molecules and on the basis of morphologies of SDS and CTAB. It is found that a small substitution of a methyl gro up by a hydrogen atom on the 3H-indole chromophore renders the probe c apable to recognize two sites in a micelle with surface roughness like SDS.