Solvent effects on rate constants for one-electron oxidation of porphyrins

Journal Article · Thu Jul 21 04:00:00 EDT 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100080a007· OSTI ID:6840933

Marguet, S; Neta, P ^[1]; Hapiot, P ^[2]

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1. National Inst. of Standards and Technology, Gaithersburg, MD (United States)
2. Universite de Paris (France)

Absolute rate constants for one-electron oxidation of free base porphyrins (hematoporphyrin-IX, mesoporphyrin-IX dimethyl ester) by the trichloromethylperoxyl radical and by the radical cation of N-methylindole have been determined in a variety of solvents by the pulse radiolysis technique. All solvents were air-saturated and contained CCl[sub 4] as a source for the CCl[sub 3]O[sub 2][sup [sm bullet]] radicals. The rate constants for reactions of these radicals were measured by following the formation of the porphyrin [pi]-radical cation optical absorption at 700 nm as a function of porphyrin concentration. The rate constants for reaction of CCl[sub 3]O[sub 2][sup [sm bullet]] with the porphyrin were found to vary by an order of magnitude in the different solvents and were correlated with the solvent cohesive energy density. In the second set of experiments, N-methylindole was used in addition to CCl[sub 4] so that CCl[sub 3]O[sub 2][sup [sm bullet]] radicals oxidize this solute to its radical cation, which in turn oxidizes the porphyrin. The variations of the rate constants for oxidation of the porphyrin by the N-methylindole radical cation in the different solvents exhibited different trends than those for oxidation by CCl[sub 3]O[sub 2][sup [sm bullet]] radicals. 39 refs., 1 fig., 6 tabs.

• OSTI ID: 6840933
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:29; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400400 -- Electrochemistry
99 GENERAL AND MISCELLANEOUS
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AZINES
CARBON TETRACHLORIDE
CARBONIC ACID ESTERS
CARBOXYLIC ACIDS
CATIONS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
COMPILED DATA
DATA
DECOMPOSITION
DMSO
ELECTRONS
ELEMENTARY PARTICLES
ENERGY
ESTERS
FERMIONS
FREE ENERGY
HALOGENATED ALIPHATIC HYDROCARBONS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
IONS
KINETICS
LEPTONS
MATHEMATICAL MODELS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDATION
PHYSICAL PROPERTIES
PORPHYRINS
PYRIDINE
PYRIDINES
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION KINETICS
SOLVENTS
SULFOXIDES
THERMODYNAMIC PROPERTIES
VOLTAMETRY