Reduction potentials of vesicle-bound viologens
- Oregon Graduate Inst. of Science and Technology, Beaverton (United States)
Thermodynamic reduction potentials have been determined by using spectroelectrochemical and cyclic voltammetric methods for a homologous series of amphiphilic ciologens (N-methyl-N{prime}-alkyl-4,4{prime}-bipyridinium ions, C{sub n}MV{sup 2+}) in a variety of media, including dihexadecyl phosphate (DHP), dioctadecylimethylammonium, and phosphatidylcholine small unilamellar vesicles. In general, potentials for both one-electron steps, i.e., C{sub n}MV{sup 2+} + e{sup {minus}} {yields} C{sub n}MV{sup +} and C{sub n}MV{sup +} + e{sup {minus}} {yields} C{sub n}MV{sup 0}, were insensitive to the alkyl chain length, which was varied over the range n = 6{minus}20. The single exception was a large decrease ({approximately}100 mV) in the first reduction potential for DHP-bound viologens when the chain length was increased from n = 10 to n = 12; this effect was attributed to a change in binding topography. The magnitudes of the reduction potentials were highly dependent upon the vesicle charge; the pattern observed indicated that interfacial electrostatic interactions between the surfactant headgroups and bipyridinium rings were the dominant factors determining the potentials. As discussed in the text, the data allow resolution of several heretofore puzzling observations concerning viologen reactivities in microphase suspensions.
- DOE Contract Number:
- FG06-87ER13664
- OSTI ID:
- 7017229
- Journal Information:
- Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:20; ISSN 0022-3654; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400400* -- Electrochemistry
ABSORPTION SPECTROSCOPY
AZINES
BIPYRIDINES
CATIONS
CHARGED PARTICLES
CHEMICAL REACTIONS
CHEMISTRY
DATA
DISPERSIONS
ELECTROCHEMISTRY
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
IONS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PYRIDINES
REDOX POTENTIAL
REDUCTION
SPECTRA
SPECTROSCOPY
SUSPENSIONS
VISIBLE SPECTRA
VOLTAMETRY