Solubilization of two cyano 3H-indole molecular probes in SDS and CTAB micelles: spectral and photophysical characterization

Abstract

An absorption and fluorescence spectral study on the solubilization behaviour of 2-[(p-amino)phenyl]-3,3-dimethyl-5-cyano-3H-indole (1) and 2-[(p-dimethylamino)phenyl]-3,3-dimethyl-5-cyano-3H-indole (2) in sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) aqueous micelles has been carried out. Using spectral correlations with polarity parameters, bandwidths and photophysical parameters, the nature of the binding site of the molecules in micelles has been discussed. Both molecules occupy sites in SDS and CTAB that are less polar than water but accessible to it. The dimethylamino substituent helps in pushing the molecule toward the micellar core in both micelles. pH effects on the ring-nitrogen protonation (neutral–monocation equilibrium) and terminal nitrogen deprotonation (neutral–monoanion equilibrium) in SDS and CTAB, respectively, have also been discussed and found to be consistent with both the pseudophase ion-exchange (PIE) and electrostatic models.