J- and H-Aggregates of Porphyrin−Surfactant Complexes: Time

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J. Phys. Chem. B 1998, 102, 1528-1538

J- and H-Aggregates of Porphyrin-Surfactant Complexes: Time-Resolved Fluorescence and Other Spectroscopic Studies† Nakul C. Maiti, Shyamalava Mazumdar, and N. Periasamy* Chemical Physics Group, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India ReceiVed: July 17, 1997; In Final Form: October 6, 1997

The interactions of several water-soluble ionic porphyrins with different ionic or neutral surfactants in aqueous solutions were studied as a function of surfactant concentration. The interaction leads to the formation of porphyrin aggregates and/or micelle-encapsulated monomers with the exception of those porphyrin-surfactant pairs for which the interaction is Coulombically repulsive. The premicellar surfactant-porphyrin aggregate is identified by absorption and fluorescence spectroscopy, fluorescence lifetime and anisotropy, and resonance light scattering. The spectroscopic results are used to characterize the premicellar aggregates as J-type, H-type, or nonspecific aggregates. All premicellar surfactant-porphyrin aggregates dissociate to form micelleencapsulated monomers when the surfactant concentration approaches cmc (critical micellar concentration). The interaction of tetrakis-(4-sulfanatophenyl)porphine dianion (H4TPPS2-) at pH