Oxidative quenching of the excited state of tris(2,2[prime]-bipyridine)ruthenium (2 +) ion by methylviologen. Variation of solution medium and temperature

Journal Article · Thu May 12 04:00:00 EDT 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100070a019· OSTI ID:7267235

Sun, Hai; Yoshimura, Akio; Hoffman, M Z ^[1]

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1. Boston Univ., MA (United States)

The rate constant (k[sub q]) for the quenching of *Ru(bpy)[sub 3][sup 2+] by methylviologen (MV[sup 2+]) has been determined as a function of the mole fraction of CH[sub 3]CN (X[sub AN]) in aqueous mixtures; k[sub q] goes through a minimum at X[sub AN] approximately 0.4, which is suggested to occur because of the dynamic solvent effect for the electron-transfer reaction in the mixed solvents, whereby the relaxation dynamics of the solvent is a strong function of its composition. The cage escape yield ([eta][sub ce]) for the release of the redox products into bulk solution has been determined as a function of ionic strength, temperature, and X[sub AN]; the apparent activation energy for the back electron transfer (E[sub bt]) between the geminate redox pair, Ru(bpy)[sub 3][sup 3+] and MV[sup [sm bullet]+], within the solvent cage produced upon quenching is obtained from the data through the application of the simple cage model. E[sub bt] is independent of ionic strength in aqueous solutions, but is strongly dependent on solvent composition in mixed solvents. However, E[sub bt] decreases smoothly from 9.6 kJ mol[sup [minus]1] in aqueous solution to -5.5 kJ mol[sup [minus]1] in CH[sub 3]CN-rich solvents as X[sub AN] is increased, requiring that a modification of the simple model be made. 26 refs., 11 figs., 3 tabs.

• OSTI ID: 7267235
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:19; 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
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
ACETONITRILE
AQUEOUS SOLUTIONS
AZINES
BIPYRIDINES
CATIONS
CHARGED PARTICLES
CHEMICAL ACTIVATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPILED DATA
COMPLEXES
DATA
DISPERSIONS
ELECTRON TRANSFER
ENERGY LEVELS
EXCITED STATES
HETEROCYCLIC COMPOUNDS
INFORMATION
IONS
KINETICS
MATHEMATICAL MODELS
MIXTURES
NITRILES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OXIDATION
PYRIDINES
QUENCHING
RADICALS
REACTION KINETICS
RUTHENIUM COMPLEXES
SOLUTIONS
TRANSITION ELEMENT COMPLEXES