MOLECULAR HYSTERESIS IN AN ELECTROCHEMICAL SYSTEM REVISITED

Earlier work on the electrochemical behavior of (1,5-dithiacyclooctane 1-oxide)bis(pentaammineruthenium) has been repeated and extended so that the kinetic and equilibrium parameters which define the ''double-block'' diagram are now determined (acetone as solvent, 20-degrees-C). The metastable fully oxidized form (Ru3+-SO/Ru3+-S) decays to the stable isomer (Ru3+-OS/Ru3+-S) at a specific rate of 13 s-1; DELTAG-degrees for the reaction is -36 kJ mol-1. The metastable fully reduced form (Ru2+-OS/Ru2+-S) decays to the stable form (Ru2+-SO/Ru2+-S) at a specific rate of 3.8 s-1; DELTAG-degrees = -55 kJ mol-1. In the mixed-valence state, (Ru3+-OS/Ru2+-S) changes to (Ru2+-SO/Ru3+-S) by intramolecular electron transfer at a specific rate of 0.12 s-1 (DELTAG-degrees = -1.9 kJ mol-1). Completion of the evaluation of the dynamic parameters was enabled by the direct determination of those cited for the mixed-valence state.