A study of the effects of polyelectrolytes on the photochemical system containing a Ru(bpy)32+ derivative, methylviologen, and ferricyanide

Abstract

A photosensitized electron-transfer system is described in which charge separation of redox products on separate like-charged polyelectrolytes is achieved and considerable retardation of their back reaction is observed. The process of quenching of a polyelectrolyte-anchored Ru(bpy)/sub 3//sup 2 +/ derivative by methylviologen (MV/sup 2 +/) and the quantum yields of electron-transfer products escaping charge recombination followed by their back electron-transfer reaction were studied. Quantum yields were found to be lower and rate constants for the back reaction about the same as the well-studied Ru(bpy)/sub 3//sup 2 +/-MV/sup 2 +/ system. The addition of Fe(CN)/sub 6//sup 3 -/ and the polyelectrolyte, polybrene, to the system was also studied. The rate of electron transfer from MV/sup +/. to ferricyanide in the presence of polybrene was measured and it was found that the rate of back electron transfer from Fe(CN)/sub 6//sup 4 -/ trapped in polybrene to the highly positively charged polyelectrolyte-anchored Ru(bpy)/sub 3//sup 3 +/ could be inhibited by more than 2 orders of magnitude compared to the rate of this reaction in homogeneous solution. This is attributed to the slow diffusion and high electrostatic repulsion between the polyelectrolyte-trapped species. The role played by counterions in this system is also critically assessedmore » and ways to achieve more effective inhibition in two-polyelectrolyte systems are discussed. 25 references, 5 figures, 4 tables.« less