Electron transfer quenching of excited pyrene or Ru(II)(bpy)3 derivative in Langmuir-Blodgett films by donor or acceptor molecules with different redox potentials

By using nanosecond laser photolysis, the luminescence decay curves were recorded for a sensitizer such as pyrene and Ru(bpy)²⁺₃ derivatices (where bpy is bypyridine) confined in one monolayer in Langmuir-Blodgett (LB) films which also contained the other monolayer of an acceptor or a donor surfactant deposited apart from the sensitizer monolayer by a fixed distance. In addition to the distinct difference of 1.0 V in the oxidation potentials between the excited pyrene and the Ru(bpy)²⁺₃ derivatives, the redox potentials of four types of acceptor and one donor used in the present study ranged widely up to 1.8 V width. This enabled us to examine the dependence of the photoinduced electron transfer rates on the standard free energy difference δG° of the reaction.

The rate constants calculated from the analysis of the decay curves will be discussed also in terms of the structure of the LB films and the distance between the sensitizer and the acceptor (or donor) monolayer.