Salt and solvent effects on the kinetics of the oxidation of the excited state of the [Ru(bpy)3]2+ complex by S2O8(2-).
The title reaction was studied in different reaction media: aqueous salt solutions (NaNO3) and water-cosolvent (methanol) mixtures. The observed rate constants, k(obs), show normal behavior in the solutions containing the electrolyte, that is, a negative salt effect. However, the solvent effect is abnormal, because a decrease of the rate constant is observed when the dielectric constant of the reaction medium decreases. These effects (the normal and the abnormal) can be explained using the Marcus-Hush treatment for electron transfer reactions. To apply this treatment, the true, unimolecular, electron-transfer rate constants, k(et), have been obtained from k(obs) after calculation of the rate constants corresponding to the formation of the encounter complex from the separate reactants, k(D), and the dissociation of this complex, k(-D). This calculation has been carried out using an exponential mean spherical approach (EMSA).
Lopes-Costa
T
T
Departamento de Química Física, Facultad de Química, Universidad de Sevilla, c/ Profesor García Gonzalez s/n, 41012 Sevilla, Spain.
Lopez-Cornejo
P
P
Villa
I
I
Perez-Tejeda
P
P
Prado-Gotor
R
R
Sanchez
F
F
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000737:chemistry; D056831:Coordination Complexes; D007700:Kinetics; D000432:Methanol / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D017670:Sodium Compounds / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D017975:Ruthenium Compounds
D015082:2,2'-Dipyridyl; D056831:Coordination Complexes; D000432:Methanol; D009566:Nitrates; D017670:Sodium Compounds; D013431:Sulfates; D014867:Water; C547232:tris(2,2-bipyridine)-ruthenium(II); D017975:Ruthenium Compounds; C031618:sodium nitrate; C024625:sodium persulfate