Studies on electrochemical properties of thionyl chloride reduction by Schiff base metal(II) complexes

Electrocatalytic effects associated with the reduction of thionyl chloride in a LiAlCl 4–SOCl 2 electrolyte solution containing Schiff base metal(II) (metal (M): Co, Ni, Cu and Mn) complexes are evaluated by determining the kinetic parameters for the reactions using cyclic voltammetry at a glassy carbon electrode. The charge-transfer process during the reduction of thionyl chloride is affected by the concentration of the catalyst. Catalytic effects are demonstrated from both a shift in the reduction potential for the thionyl chloride in a more positive direction and an increase in peak currents. The reduction of thionyl chloride is diffusion controlled. Catalytic effects are larger for thionyl chloride solutions containing M(II)(1,5-bis(salicylidene imino) pentane) (M(II)(SALPE)) rather than M(II)(1,3-bis(salicylidene imino) propane) (M(II)(SALPR)). Significant improvements in cell performance are found in terms of the both thermodynamics and kinetic parameters for the thionyl chloride reduction. An exchange rate constant, k 0, of 1.89×10 −8 cm s −1 is found at the bare electrode, while larger values of 2.79×10 −8 to 2.09×10 −6 cm s −1 are observed in the case of the catalyst-supported glassy carbon electrode.