One-electron reduction of dihexadecyl phosphate vesicle bound viologens bypentacyanocobaltate(II) ions
N-Methyl-N'-alkyl-4,4;-bipyridinium (C/sub n/MV/sup 2 +/) ions bound to dihexadecyl phosphate (DHP) vesicles are rapidly reduced to radical cations by Co(CN)/sub 5//sup 3 -/ in alkaline solutions containing cyanide ion. For the short-chain viologens investigated (n less than or equal to 10), the predominant pathway obeys the rate law d(C/sub n/MV/sup +/)/dt = a(C/sub n/MV/sup 2 +/)/(b + c(C/sub n/MV/sup 2 +/)), where a is pseudo first order in (Co(CN)/sub 5//sup 3 -/) and (CN/sup -/) under the experimental conditions. Reaction rates for longer chain viologens (n greater than or equal to 14) are several-fold slower at comparable reactant concentrations; the kinetic traces are biphasic, with both components first order in (C/sub n/MV/sup 2 +/) and pseudo first order in (Co(CN)/sub 5//sup 3 -/) and (CN/sup -/). A mechanism consistent with the data comprises outer-sphere electron transfer preceded by Co(CN)/sub 4//sup 3 -/ ligation of a sixth CN/sup -/ ion. This mechanism was confirmed for C/sub 6/MV/sup 2 +/-DHP vesicles by quantitative isolation and spectrophotometric identification of Co(CN)/sub 6//sup 37/ ion as the Co(III) product. The biphasic reduction of the long-chain viologens was taken as evidence for two distinct binding environments within DHP vesicles. The significance of these findings is discussed with the context of other studies on the dynamic properties of C/sub n/MV/sup 2 +/-DHP particles. 25 references, 4 figures, 1 table.
- Research Organization:
- Oregon Graduate Center, Beaverton
- DOE Contract Number:
- AC06-83ER13111
- OSTI ID:
- 6950562
- Journal Information:
- Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 26:1; ISSN INOCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
AZINES
BIPYRIDINES
CHEMICAL REACTIONS
COBALT COMPOUNDS
CYANIDES
DATA
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
MEMBRANES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PYRIDINES
REDUCTION
TRANSITION ELEMENT COMPOUNDS