Kinetics and Mechanisms of the Reduction of Cobalt(II) 4,4',4'',4'''-Tetrasulfophthalocyanine by 2-Mercaptoethanol under Anoxic Conditions

Article abstract of DOI:10.1021/j100338a083

The kinetics and mechanism of reduction of cobalt(II) 4,4',4'',4'''-tetrasulfophthalocyanine by 2-mercaptoethanol to yield cobalt(I) tetrasulfophthalocyanine and 2-hydroxyethyl disulfide under anoxic conditions were investigated and the following rate law was found: ν = -dIITSP>_T/dt = 2K_1TIITSP>_T>/<2(1 + a_H+/K_a1 + K_a2/a_H+)(1 + α_T)>, where k₂ is a rate constant for the rate-limiting electron-transfer step, and K₁ is the equilibrium constant for the complexation of a CoTSP dimer with thioethanol; K_a1 and K_a2 are the apparent acid dissociation constants of HOC2H4SH and HOC2H4S^-, respectively; α is K₁/(1 + a_H+/K_a1 + K_a2/a_H+); a_H+ is the hydrogen ion activity.A nonlinear least-squares fit of the experimental data to the above rate law gave k₂ = 228 +/- 3.8 s^-1 and K₁ = 117 +/- 2.5 M^-1 at 27 deg C at μ = 0.4 M.