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), Vol. 85:23
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BIPYRIDINES
SCINTILLATION QUENCHING
PALLADIUM COMPLEXES
PHOTOLYSIS
PORPHYRINS
AQUEOUS SOLUTIONS
DETERGENTS
ELECTRON TRANSFER
EXPERIMENTAL DATA
FLUORESCENCE
LASER RADIATION
MICELLAR SYSTEMS
PULSED IRRADIATION
REDOX REACTIONS
ADDITIVES
AZINES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COMPLEXES
DATA
DECOMPOSITION
DISPERSIONS
ELECTROMAGNETIC RADIATION
EMULSIFIERS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
IRRADIATION
LUMINESCENCE
MIXTURES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PYRIDINES
RADIATIONS
SOLUTIONS
SURFACTANTS
TRANSITION ELEMENT COMPLEXES
WETTING AGENTS
400500* - Photochemistry