Yoshikiyo Kato

Reversible half-wave potentials of reduction processes on nitroxide radicals

Abstract The reversible half-wave potential ( E 1 2 rev ) of the reduction process was determined for six nitroxide radicals by cyclic voltammetry as the midpoint potential between reduction and reoxidation peaks. The variations of E 1 2 rev with pH were interpreted as the protonation induced by the one-electron reduction of nitroxide radicals.

Substituent effects of cis-dioxobis(dithiocarbamato) molybdenum(VI) on redox properties: redox potentials for one-electron reduction and second-order rate constants for oxygen atom transfer

Abstract The electrochemical properties of a series of cis-dioxobis(dithiocarbamato)molybdenum(VI) complexes [MoO2(RR′dte)2] (RR′dte = N,N-disubstituted dithiocarbamate) and the oxygen atom transfer reactions between [MoO2(RR′dte)2] and PPh3 in 1,2-C2H4Cl2 at 25°C are systematically investigated. A good correlation between logarithmic values of second-order rate constants k1 of the oxygen atom transfer reactions and redox potentials E°′ for [MoO2OP2RR′dte)2]01couples is observed over the wide range of k1 (from 0.012 to 0.61 M s+2); the values of log k1 linearly increase with the increase of E0. The departure from the correlation line is exactly observed for [MoO2(Bz2dte)2/PPh2 [MoO2(Ph2dte)2]/PPh1 and [MoO2(BzPhdte)2]PPh1 systems. A negative activation entropy (ΔS′ = −114 J mol+1K+1) of the oxygen atom transfer reaction obtained for the [MoO2(Et2dte)2]/PPh4 system indicates that the reaction proceed through an associative process. These results suggest that an attack of a lone pair of PPh4 on an oxo ligand and a negative charge flow to the molybdenum center occurs to form an activated complex. The anomaly observed for [MoO2(Bz2dte)2]/PPh4, [MoO2(Ph2dte)2]/Pph4 and [MoO2(RR′dte)2]. Other physicochemical properties of the complexes such as 11C NMR and Mo O stretching frequencies in solutions and the X-ray crystal structure of cis-dioxibis(thiomorpholydithiocarbamato)molybdenum(VI) are also reported.

Correlation between 95Mo NMR chemical shifts and rate constants of oxygen atom transfer reactions of various cis-dioxobis(dithiocarbamato)molybdenum(VI) complexes with PPh3

Abstract The 95 Mo NMR properties of cis -dioxomolybdenum(VI) complexes with various dithiocarbamates [MoO 2 (R 2 dtc) 2 ] (R 2 dtc − : dithiocarbamates, R = CH 3 , C 2 H 5 i-C 3 H 7 , i-C 4 H 9 , C 6 H 5 , C 6 H 5 CH 2 ) have been investigated. The chemical shifts varied from δ = 151 (R = CH 3 ) to δ = 216 (R = i-C 3 H 7 ) depending on the nature of the substituents on the dithiocarbamate ligands, and they were found to be in a good correlation with the rate constants for the oxygen atom transfer reaction between [MoO 2 (R 2 dtc) 2 ] and triphenylphosphine in 1,2-C 2 H 4 ,Cl 2 .

Component distribution in plasma-deposited ultrafine powders of binary (Cr2O3, Fe2O3, SnO2)–Al2O3 systems

Ultrafine powders of the binary (Cr2O3, Fe2O3, SnO2)–Al2O3 systems were synthesized by introducing aqueous solutions containing metal salts into a high temperature inductively coupled plasma, and the distribution of component oxides was investigated by transmission electron microscopy and electrophoretic mobility measurements. For the Cr2O3–Al2O3 system, each component independently constituted its particles that were homogeneously distributed in the powder. With the Fe2O3Al2O3, the two components formed solid solutions. In the SnO2–Al2O3, each component comprised the powders where SnO2 had a strong tendency to occupy the particle surface.

Conductometric determination of thermodynamic successive ionization constants of chloranilic acid

Abstract The thermodynamic successive ionization constants of chloranilic acid were determined by the least square fitting between experimental molar conductivities and the theoretical ones. The theoretical molar conductivities are numerically calculated. The values of p K ° a1 for the ionization and p K ° a2 for the second were found to be 1.73 and 3.01, respectively.