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Gated redox reactions involving the [[Cu[(dmp).sub.2](solvent)].sup.2+]/[[Cu[(dmp).sub.2]].sup.2+] couple (dmp=2,9,dimethyl-1,10-phenanthroline) in acetonitrile were investigated at elevated pressures. The results led to conclusion that the reverse cross-reaction of the gated reduction of the [[Cu[(dmp).sub.2](solvent)].sup.2+]/[[Cu[(dmp).sub.2]].sup.2+] couple proceeds through the product excited state while the direct self-exchange reaction proceeds through an ordinary process.

Substitution-inert Co(II) complex with tropidal 1,1,1-tris (dimethylphosphinomethl) ethane were produced in aqueous solution by the controlled-potential electrolysis. EPR studies indicated that the Co(II)[P.sub.6] and Co(II)[P.sub.3][S.sub.3] species are in the low-spin [t.sup.6.sub.2g][e.sup.1.sub.g] state. The analyses of the absorption spectra of the Co(II) species in solution indicated significant Jahn-Teller distortion in Co(II) [P.sub.6] and Co(II)[P.sub.3][S.sub.3] ions as expected for the low-spin [d.sup.7] electronic configuration, while less distortion was observed for the Co(II)[S.sub.6] ion. Kinetic studies of the redox reactions involving these Co(III/II) specipies confirmed that the electron self-exchange reactions for the (III/II)[P.sub.6] and Co(III/II)[P.sub.3][S.sub.3] couples are relatively fast ([k.sub.ex] ~ 1 x [10.sup.4][dm.sup.3][mol.sup.-1][s.sup.-1]), which is consistent with the results for the low-spin Co(III/II) couples. It was concluded that the nephelauxautic effect of the P-donor atom stabilizes the low-spin state in Co(II), and that the rather rapid electron exchange rates for these Co(III/II) couples were explained by the lack of the spin reorganization process required for the ordinary low-spin--high-spin Co(III/II) couples. Key words: cobalt(III/II), spin state, EPR study,, kinetics, electron transfer

The gated behavior of copper(II) and -(I) species was interpreted by assessing the reduction reactions of bis(2,9-dimethyl-1,10-phenanthroline)copper(I/II) in acetonitrile. A consistency was noted between the electron self-exchange rate constants estimated for the Cu(dmp)(sub 2)(super 2+/+) couple and the directly measured value by NMR(5 X 10 cubed kg mol-1 s-1). The electron self-exchange rate constant of Cu(dmp)(sub 2)(super 2+/+) as 1.6 kg mol-1 s-1 from the reduction of Cu(dmp)(sub 2)(super 2+) by Co(bpy)(sub 3)(super 2+) was obtained.

Marcus-Hush theory is applied to outer sphere self-exchange electron transfer reactions, in which there is a net chemical change. The result shows the importance of the volume cross relation for reactions with moderate DeltaE. This volume cross relation offers a way of deriving experimentally inaccessible volumes of activation but fails at high driving forces.

Outer sphere oxidation reactions of L-ascorbic acid by the hexacyanometalate(III) ions in aqueous acid medium indicate that the oxidation reactions are not a simple adiabatic process. It is a complex process with a bicylic intermediate, and the electron enhance rate constants for the couple HAsc./HAsc- are determined. All these oxidation reactions are analyzed at elevated pressures.

The kinetics of the homogeneous self-exchange reaction of Fe(Cn)6(super 3-/4-) in aqueous K+ media with (C6H5)4As+ as support is investigated. The analysis shows that the path for electron transfer is composed of three K+ ions. The influence of pressure on the homogeneous exchange reaction is determined to be DeltaV(sub ex) = +22 plus or minus 2 cubic centimeter per mole.