Electrochemical Behavior of a New Precursor for the Design of Poly[Ni(salen)]-Based Modified Electrodes

Abstract

We describe the potentiodynamic preparation and subsequent characterization of poly[Ni(3-MeOsaltMe)] films (surface concentration, 3 < i/nmol cm -2 < 350) in acetonitrile media. Coulometric and gravimetric (electrochemical quartz crystal microbalance, EQCM) data allow one to monitor the deposition process and show that the resultant films are physically and chemically stable. Combined EQCM/probe beam deflection measurements were used to quantify the individual contributions (fluxes and population changes) of anions, cations, and solvent to the overall redox switching process. The first redox cycle for a film “rested” in the reduced state results in accumulation of anion (charge) and solvent in the film. The subsequent steadystate response is dominated by a combination of anion and solvent transfers; this takes place in two stages, the second of which involves significantly more solvent entry, to an extent dependent upon time scale. After a sequence of redox cycles, the initial thermodynamically “irreversible” behavior is restored by “resting” the film. Solvation effects are critical determinants of film redox chemistry and dynamics: in addition to controlling the feasibility and stability of deposition, they control film ion transport rate.