Intramolecular electron transfer in the reaction of hydroxyl radicals with (pyridine)pentaamminecobalt(III) ion in aqueous solution

Journal Article · Sat Sep 01 04:00:00 EDT 1979 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic50199a030· OSTI ID:6014861

Hoffman, M Z ^[1]; Kimmel, D W; Simic, M G

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1. Boston Univ., MA

The reaction of radiation-generated OH radicals with Co(NH/sub 3/)/sub 5/py/sup 3 +/ in aqueous solution to form Co/sup 2 +/(aq) serves as a model of induced electron transfer. The yield of Co/sup 2 +/(aq) formation is dependent upon the radiation dose rate, pH, and the gas used to purge the solutions (N/sub 2/O, N/sub 2/, O/sub 2/). The initial reaction of OH with Co(NH/sub 3/)/sub 5/py/sup 3 +/ (k = 6.5 x 10/sup 8/ M/sup -1/ s/sup -1/) involves addition of the radical to the aromatic ligand; pulse radiolysis reveals the absorption spectrum of this Co(III)-coordinated ligand-radical species (I) (lambda/sub max/ 325 nm, epsilon/sub max/ 1.7 x 10/sup 3/ M/sup -1/ cm/sup -1/) and shows that it is readily scavenged by O/sub 2/ (k = 4.4 x 10/sup 8/ M/sup -1/ s/sup -1/). Species I is converted (k = 8.5 x 10/sup 3/ s/sup -1/) into a similarly coordinated ligand-radical species (II), possibly via solvent-assisted ligand modification. Species II undergoes bimolecular decay (2k = 3.6 x 10/sup 5/ M/sup -1/ s/sup -1/) in competition with a deprotonation reaction with OH- (k = 1.8 x 10/sup 8/ M/sup -1/ s/sup -1/) and ligand-to-metal intramolecular electron transfer to form Co/sup 2 +/(aq) (k = 2.3 x 10/sup -2/ s/sup -1/). The deprotonated coordinated ligand radical undergoes bimolecular decay (2k = 3.8 x 10/sup 7/ M/sup -1/ s/sup -1/) in competition with intramolecular electron transfer to form Co/sup 2 +/(aq) (k = 1.1 x 10/sup 1/ s/sup -1/). A comparison of these intramolecular electron rate constants is made with those that have been obtained for other ligand radicals coordinated to Co(III) centers.

• OSTI ID: 6014861
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 18:9; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400600* -- Radiation Chemistry
AMMONIA
AZINES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COBALT COMPLEXES
COMPLEXES
DATA
DATA FORMS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
EXPERIMENTAL DATA
GAMMA RADIATION
HETEROCYCLIC COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
HYDROXIDES
INFORMATION
IONIZING RADIATIONS
ISOLATED VALUES
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PYRIDINE
PYRIDINES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADIOLYSIS
TRANSITION ELEMENT COMPLEXES
WATER