Electrocatalytic oxidation of benzyl alcohol with a monooxoruthenium(V) complex in solution and inside Nafion films

The monooxoruthenium(V) complex [Ruv(L)(O)]2+(LH = bis(2-(2-pyridyl)ethyl) (2-hydroxy-2-(2-pyridyl)ethyl)amine) is an active catalyst for the electrooxidation of benzyl alcohol in solution. The second order rate constant for the reaction between [Ruv(L)(O)]2+and benzyl alcohol evaluated by rotating disc voltammetry is 1.7 × 102mol-1dm3s-1. The activity of the catalyst is retained when immobilized inside Nafion films. However, in aqueous acidic medium the oxidation of [RuIII(L)(H2O)]2+to [Ruv(L)(O)]2+is kinetically slow within Nafion. When the pH of the medium is raised from acidic to neutral, oxidation of the complex inside Nafion becomes more facile and the activity of the modified electrode towards alcohol oxidation increases. The partitioning of the catalyst in different phases of the Nafion film appears to depend on pH, with part of the immobilized complexes staying in an "electroinactive" region in neutral supporting electrolytes. The catalyst gradually becomes deactivated during the course of alcohol oxidation.