Kinetics of Redox Processes in the Polymer Films of Ni(II) Salen Type Complexes

The voltammetry and chronocoulometry methods were used in the research of kinetics of redox processes occurring on electrodes modified with conductive polymers, derived from the following complexes: (+/-)-trans-N,N'-bis(salicylidene)-1,2-cyclohexanediaminenickel(II) (poly[Ni(salcn)]), ((+/-)-trans-N,N'-bis(3,-methylsalicylidene)-1,2-cyclohexanediaminenickel(II) (poly[Ni(salcn(Me))]) and ((+/-)-trans-N,N'-bis(3,-tert-butylsalicylidene)-1,2-cyclohexanediaminenickel(II) (poly[Ni(salcn(Bu))]). Spectroelectrochemical method and chronopotentiometry were used to determine the mechanisms of redox processes. In poly[Ni(salcn)] and poly[Ni(salcn(Bu))] the ligand is oxidized, whereas in poly[Ni(salcn(Me))] both the ligand and the central ion are oxidized. The processes take place according to the EE mechanism. The poly[Ni(salcn)] and poly[Ni(salcn(Me))] films of thickness obtained as a result of 1-30 electropolymerization cycles, as well as poly[Ni(salcn(Bu))] of thickness obtained as a result of up to 150 cycles were studied. The investigated films of each complex are limited by surface processes, diffusion and surface-diffusion processes, depending on the film thickness. For the films that generate surface-diffusion processes, the boundaries of such processes have been determined. For the diffusion processes, the boundaries of semi-infinite diffusion regime and finite diffusion regime have been defined. On this basis, the cD1/2 value for anode and cathode processes providing semi-infinite diffusion conditions has been determined as a criterion for selection of the optimal conditions for modification of the electrodes. (C) 2019 The Electrochemical Society.