Facilitated proton transfer via water autoprotolysis-electron transfer coupled reactions at thick-film modified electrodes

Abstract

We present the derivation of a general mathematical model for facilitated proton transfer (FPT) reactions across a liquid|liquid (L|L) interface assisted by a protonatable neutral weak base at a thick organic film modified electrode setup. The effect of the explicit consideration of water autoprotolysis is analysed. The model reported in this paper allows us to simulate the system under different experimental conditions, such as initial pH, organic phase to aqueous phase volume ratio and concentration of redox probe and transferring protonated species. This model for the FPT reactions via water autoprotolysis in a system with two polarized interfaces is compared to our previous results calculated for a single polarizable interface [J. Electroanal. Chem. 578 (2005) 159–170]. We simulate a system with a single redox probe with two reversible non-simultaneous reduction processes with the goal of obtaining detailed mechanistic information of the facilitated proton transfer via water autoprotolysis process at thick-film modified electrodes. Our conclusions can be straightforwardly applied in experiments. We focus on a system consisting of 7,7,8,8-tetracyanoquinodimethane (TCNQ) as a redox probe and 2,9-dimethyl-1,10-phenanthroline (2,9-DMP) as a neutral weak base.