Thermodynamic study of the interaction between 5,10,15,20-tetrakis-(N-methyl-4-pyridyl)porphyrin tetraiodine and sodium dodecyl sulfate

Abstract The interaction between 5,10,15,20- tetrakis -( N -methyl-4-pyridyl)porphyrin tetraiodine (TMePyPI 4 ) and the anionic surfactant sodium dodecyl sulfate (SDS) has been studied in aqueous solutions using electrical conductivity, UV–vis and fluorescence spectrophotometries. The electrical conductivity data suggests that the addition of SDS to TMePyPI 4 solutions is accompanied by strong interactions (mainly electrostatic) with the formation of aggregates. These aggregates have a stoichiometry somewhat lower than the simple charge neutralization, possible due to the formation of supramolecular structures. At SDS/TMePyPI 4 ratios higher than the stoichiometry ratio, those SDS-TMePyPI 4 redissolve and at higher SDS concentrations formation of micelles is observed. The effect of both porphyrin surfactant and temperature allows a detailed thermodynamic analysis of the SDS micellization process in this multicomponent system.