MEDIUM EFFECTS ON THE ELECTRON-TRANSFER REACTION BETWEEN EXCITED SINGLET PYRENE AND INDOLE

The kinetics of the electron transfer reaction between excited singlet pyrene derivatives and indoles has been investigated in several media. In homogeneous solvents the bimolecular rate constant increases with the solvent macroscopic dielectric constant. This seems to be a general behavior independent of the solvent microscopic structure, except for the most efficient quenchers in which the diffusional contribution becomes important. The charge separation efficiency was also investigated in homogeneous solvents. It was found that the changes observed may be explained by the trend in the cage escape rate constant according to the Eigen's model. The electron transfer step in some cases is followed by a proton transfer process which leads to a photochemical reaction. The effect of normal micelles on this reaction was investigated. Also the effect of reverse micelles and polyelectrolytes on the efficiency of the quenching was studied. It was found that the reaction can be controlled by employing derivatives of both the quencher and quenchee that are localized in known regions of the organized system.