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 micelle-encapsulated monomers when the surfactant concentration approaches cmc (critical micellar concentration). The interaction of tetrakis-(4-sulfanatophenyl)porphine dianion (H4TPPS2-) at pH <3.5 with cetyltrimethylammonium cation (CTAB) is described by the fo...

J- and H-aggregates of porphyrin-surfactant complexes: time-resolved fluorescence and other spectroscopic studies

Fluorescence decay dynamics and structure of a meso-tetrakis(p-sulfonatophenyl)porphyrin, referred to herein as either H2TSPP4- or TSPP, which aggregates in highly acidic homogeneous solution, are discussed. The fluorescence lifetime of the aggregate is found to depend on whether electronic excitation is to the B (Soret) state or the Q state. This finding is interpreted as indicating that the aggregate's effective size differs in the two cases. Also, a discussion is provided of possible nonradiative pathways that might affect measured fluorescence lifetimes. Specific structural changes that occur within the porphyrin upon N-protonation and incorporation within the aggregate are also discussed. Additionally, vibrational frequencies are assigned to specific bonds of the porphinato macrocycle, and comparisons are made between bond lengths in the aggregate environment and those of the monomeric dianion.

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Fluorescence Decay Kinetics and Structure of Aggregated Tetrakis(p-Sulfonatophenyl)Porphyrin

Porphyrin assemblies as chemical sensors

The chlorophyll triplet state as a probe of structure and function in photosynthesis.

Template-Imprinted Chiral Porphyrin Aggregates

Excited-state properties of water-soluble porphyrin dimers

The solution structures of dimers consisting of negatively charged Zn[tetra(4-carboxyphenyl)porphyrin], ZnTPPC, with positively charged Zn[tetra(4-N-methylpyridyl)porphyrin], ZnTMPyP, and with H2[tetra(4-N-methylpyridyl)porphyrin], H2TMPyP, were determined by 1H NMR ring current shifts. The conformation is not affected by the presence of the metal in the centre of the TMPyP monomer. The dimers have a cofacial conformation with a plane-to-plane separation of 3.1 A and an in-plane translation of 4.2 A along the aryl—aryl axis.

Solution structure of porphyrin aggregates determined by 1H NMR ring current shifts. I. Heterodimers of oppositely charged porphyrins

The aggregation of the water-soluble porphyrins tetra(4-carboxyphenyl)porphyrin free base (H2TPPC), tetra(4-N-methylpyridyl)porphyrin free base (H2TMPyP) and their zinc derivatives (ZnTPPC and ZnTMPyP) was studied by 1H NMR and optical absorption spectroscopy. In the solvent H2OCH3OH (4:1), mixing of the anionic H2TPPC or ZnTPPC with the cationic H2TMPyP or ZnTMPyP yields various types of “hetero” aggregates. Only H2TPPC forms “homo” aggregates in this solvent. Addition of 1 m KCl results in an increase in the aggregation of H2TPPC and also enhances the aggregation of ZnTPPC. The structures of the “hetero” aggregates are stacks of the oppositely charged porphyrins in an alternating order. However, when one of the constituents is H2TPPC, aggregates having structures of the “homo” type are also formed. The 1H NMR ring current shifts are accounted for by identical conformations of dimers, and dimer structures in trimers and higher aggregates of the “hetero” type.

Solution structure of porphyrin aggregates determined by 1H NMR ring current shifts. II. Conformations of dimers and higher aggregates of water‐soluble porphyrins

U. Hofstra

Papers

Excited-state properties of water-soluble porphyrin dimers

Solution structure of porphyrin aggregates determined by 1H NMR ring current shifts. I. Heterodimers of oppositely charged porphyrins

Solution structure of porphyrin aggregates determined by 1H NMR ring current shifts. II. Conformations of dimers and higher aggregates of water‐soluble porphyrins

Photoinduced electron transfer and spindynamics in photosynthetic model systems.