Electrical-field-driven electron self-exchange in a mixed-valent osmium(II/III) bipyridine polymer. Solid-state reactions of low exothermicity

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100348a043· OSTI ID:6831496

Jernigan, J C; Surridge, N A; Zvanut, M E; Silver, M; Murray, R W ^[1]

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1. Univ. of North Carolina, Chapel Hill (USA)

The dynamics of electrical-field-driven solid-state electron transfers between Os(II) and Os(III) sites in the 1:1 mixed-valent redox polymer poly(Os(II/II)(bpy){sub 2}(vpy){sub 2})(ClO{sub 4}){sub 25} (bpy = bipyridine; vpy = vinylpyridine) are described. The nonlinear molecular conductivity of the polymer is modeled as an experimentally controllable intersite free energy gradient imposed by the electrical field. Electron self-exchange rates are analyzed as a function of free energy and temperature from 83 to 295 K with both classical and semiclassical electron-transfer theories. The analysis shows that room-temeprature electron transfers lie near the high-temperature limit of classical behavior with a thermal barrier of 7-8 kcal/mol, but those at lowered temperature exhibit non-Arrhenius behavior and involve a nuclear tunneling mechanism. A single-frequency vibronic model gives 250 cm{sup {minus}1} as the vibrational energy and ca. 7 cm{sup {minus}1} as the electronic coupling term H{sub AB}. We derive an apparent intersite reaction free energy that is 3-8 times larger than those estimated from the applied voltage bias {Delta}E divided by the number of monolayers of osmium complex sites in the film. This effect may arise from imperfections in contacting electrodes to the 100-500-nm mixed-valent film or from a dispersion of barrier heights caused by clustering in the polymer structure or from nonscreened Coulombic interactions.

• OSTI ID: 6831496
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 93:11; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360100* -- Metals & Alloys
360104 -- Metals & Alloys-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
DATA
ELECTRON TRANSFER
EXPERIMENTAL DATA
INFORMATION
LOW TEMPERATURE
MEASURING INSTRUMENTS
MEASURING METHODS
NUMERICAL DATA
OSMIUM COMPOUNDS
POLYMERS
REFRACTORY METAL COMPOUNDS
TRANSITION ELEMENT COMPOUNDS