INTERACTIONS BETWEEN AN ANIONIC PORPHYRIN AND CATIONIC SURFACTANTS IN WATER

Interactions between decyl-, dodecyl-, and tetradecyltrimethylammonium bromide (DeTAB, DTAB, and TTAB) and an anionic porphyrin, 5,10,15, 20-tetrakis(4-sulfonatophenyl)porphine (H2TPPS4-), have been studied in water at 298.2 K. Precipitate formation constants between the surfactant cations and the H2TPPS4-anion have been obtained. The precipitates were resolubilized by a further addition of the surfactants at concentrations close to the critical micelle concentrations (cmc) in DeTAB, and below the cmc's in DTAB and TTAB solutions. Surface tension and conductance measurements show that the effects of H2TPPS4- on the cmc's are very small. The fluorescence of H2TPPS4- is quenched in both water and sodium dodecyl sulfate solutions by the methylviologen cation, but not in cationic surfactant solutions. The diffusion coefficients were measured in a system containing H2TPPS4- and TTAB; the results show the existence of large premicellar aggregates.