Photoinduced redox reactions in aqueous micelles. Quenching, back-reaction, and competing processes for tetraanionic porphyrins with alkylviologens
Photoinduced redox reactions employing the anionic porphyrins meso-tetrakis(p-sulfonatophenyl)porphyrin (1) and its palladium(II) complex (2) as excited substrates and various alkylviologens as quenchers have been studied in homogeneous aqueous solution and in the presence of the charged detergents sodium dodecyl sulfate (SDS) and cetyltrimethylammonium chloride (CTAC) above the critical micelle concentration (cmc). In homogeneous solution strong ground-state association between the porphyrins and the viologens occurs; even dynamic quenching processes result in no separation of electron transfer product ions. Addition of either SDS or CTAC reduces the quenching rates but allows the detection of product ions surviving up to ca. 100 ms in some cases. The back-reactions are sensitive to a variety of factors including added electrolyte, hydrophobicity of the viologen and its one-electron reduction product, and the charge on the surfactant. The long-lived products can be selectively intercepted by a variety of reagents. In the case of quenching of the palladium porphyrin (2) by methylviologen, the oxidized porphyrin can be reduced by iodide while the reduced viologen can be oxidized via either a colloidal catalyst or reaction with molecular oxygen. These reactions illustrate the possibility for obtaining net chemical conversion in a process whereby both the light-absorbing substrate and the quencher are recycled.
- Research Organization:
- Univ. of North Carolina, Chapel Hill
- OSTI ID:
- 6071427
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 85:23; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400500* -- Photochemistry
ADDITIVES
AQUEOUS SOLUTIONS
AZINES
BIPYRIDINES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COMPLEXES
DATA
DECOMPOSITION
DETERGENTS
DISPERSIONS
ELECTROMAGNETIC RADIATION
ELECTRON TRANSFER
EMULSIFIERS
EXPERIMENTAL DATA
FLUORESCENCE
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
IRRADIATION
LASER RADIATION
LUMINESCENCE
MICELLAR SYSTEMS
MIXTURES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PALLADIUM COMPLEXES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PORPHYRINS
PULSED IRRADIATION
PYRIDINES
RADIATIONS
REDOX REACTIONS
SCINTILLATION QUENCHING
SOLUTIONS
SURFACTANTS
TRANSITION ELEMENT COMPLEXES
WETTING AGENTS