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The reversible one-electron-transfer reactions of the following cation radicals were studied by temperature-jump and stopped-flow methods: phenothiazine (PhZ)/N,N,N′,N′-tetramethyl-p-phenylenediamine cation (TMPD\underset.+), PhZ/N,N-dimethyl-p-phenylenediamine cation (DMPD\underset.+), DMPD/TMPD\underset.+ and DMPD/N,N,N′,N′-tetramethylbenzidine cation (TMBZ\underset.+). The solvent used was either 1 : 3 ethanol-water or acetonitrile. For PhZ/TMPD\underset.+, PhZ/DMPD\underset.+ in ethanol-water and also for DMPD/TMPD\underset.+ in acetonitrile, the backward reaction corresponding to the negative free energy change of reaction (ΔF°

The title complex (I) was resolved on a chromatographic column of A- tris(l,10-phenanthroline)ruthenium(ID-montmorillonite.

The monomer-dimer equilibrium of RhCl(PPh3)3 in benzene has been studied with a stopped-flow apparatus under He gas pressure. The decomposition rate of a dimer, [RhCl(PPh3)2]2, obeys pseudo-first-order kinetics with respect to the concentration of PPh3, whereas the formation rate of a dimer obtained by diluting an equilibrium solution with benzene depends on the equilibrium concentration of a monomer, a dimer and PPh3 in a complexed manner. The kinetic results are consistent with the following mechanism; 2RhCl(PPh3)3\ightleftarrowsRhCl(PPh3)2+RhCl(PPh3)3+PPh3\ightleftarrows[RhCl(PPh3)2]2+2PPh3.

Rate constants were obtained with a temperature-jump apparatus for the electron-transfer reaction between 7,7,8,8-tetracyanoquinodimethane anion radical and 2,3-dichloro-5,6-dicyano-p-benzoquinone in acetonitrile/ tetrahydrofuran (MeCN/THF) and in acetonitrile/water (MeCN/H2O) mixtures. In MeCN/THF, the forward rate constant (k) was determined in three kinds of mixed solvents: k=(5±2)×109 M−1s−1 (pure MeCN), (2.2±0.2)×109 M−1s−1 (1: 2 MeCN/THF), and (6±2)×108 M−1s−1 (1: 10 MeCN/THF) at 25±2°C. In MeCN/H2O the forward rate constant increases with the square of the H2O concentration in the range of [H2O]=2–10 M; k=k0[H2O]2 with k0=(1.0±0.2)×106 M−3s−1 at 25±2 °C. The results are discussed in terms of the specific solvation and the ion-pairing of ion radicals.

The protonation of TCNQ, anion radical has been studied with an oxygen-free stopped-flow apparatus. The protonation rate is proportional to the square of TCNQ\ewdot concentration, being independent of the proton concentration. It is suggested that there exists an intramolecular step in which the electronic structure of TCNQ\ewdot changes into another one ready to accept a proton.

Etudes, a l'aide de mesures de spectres electroniques, de dichroisme electrique et de dichroisme circulaire, de l'adsorption d'un complexe metallique, optiquement actif sur une particule colloidale de montmorillonite sous forme Na. Le compose d'addition de l'argile avec le Λ-tris-(phenanthroline-1,10) ruthenium(II), (Λ-Ru(phen) 3 2+ ) admet l'adsorption de Δ-M(phen) 3 2+ , (M=Ru, Fe, Ni), mais pas celle de Λ-M(phen) 3 2+ en exces par rapport a la capacite d'echange de cations. Par suite d'une telle adsorption stereospecifique, les melanges racemiques des complexes metalliques labiles, tels que Co(phen) 3 2+ et Fe(phen) 3 2+ sont antiracemises en presence de Λ-Ru(phen) 3 2+ -montmorillonite (ou Δ-Ni(phen) 3 2+ -montmorillonite). Lorsqu'une molecule achirale, comme le cation Orange d'acridine est adsorbe sur Δ-Ni(phen) 3 2+ -montmorillonite, il y a induction d'activite optique dans le spectre electronique de l'adsorbat

The reversible dimerization of the anion radical of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) has been studied in water, acetonitrile (MeCN), and other organic solvents. The analysis of the thermodynamic parameters of dimerization equilibria reveals that a large negative entropy term plays a primary role in determining the equilibrium constants. The temperature-jump measurement shows that the forward rate constant in water containing 5.8 M urea is nearly a diffusion controlled one, (1±0.5)×108 M−1 s−1 at −6°C. In MeCN-water mixtures, the backward reaction rate increases with the square of the MeCN concentration. This result suggests that a dimer is effectively decomposed by the successive attacks of the two MeCN molecules.

The kinetics of the protonation of sodium salt of 7,7,8,8-tetracyanoquinodimethane (Na+TCNQ\ewdot) by hydrogen chloride in alcohols and acetonitrile was investigated, using a stopped-flow apparatus. In methanol, the protonation rate is first-order in HCl and second-order in Na+TCNQ\ewdot, while in ethanol, the rate is one-half-order in HGl and second-order in Na+TCNQ\ewdot. The protonation rate in acetonitrile is first-order in HCl, but it deviates from second-order in Na+TCNQ\ewdot. These results are interpreted in terms of the rapid formation of a protonated intermediate in the initial stage of the reaction, according to TCNQ\ewdot+H+\ightleftharpoonsHTCNQ\ewdot The reversibility of this reaction is well demonstrated by the second-order dependence of the rate on Na+TCNQ\ewdot. The rate is also compared with the protonation rate of semiquinones, such as sodium salts of p-chloranil and 2,3-dicyano-l,4-benzoquinone, from the view point of the difference in reactivity between carbon and oxygen acids.