Photochemically induced energy-transfer effects on the decay times of ruthenium complexes in polymers

The effects of photobleaching on absorption properties and decay times of ruthenium complexes adsorbed on silica gel or dissolved in polystyrene or PVC are reported. While complexes with bipyridyl ligands adsorbed on silica gel did not show any decay time decrease at all, complexes having phenanthroline ligands exhibit a significant photodegradation which is manifested not only by a decrease in luminescence intensity but also by decay time decrease and specific absorption spectral changes. The effects are shown to depend strongly on the oxygen and dye concentrations present at the bleaching process. The absorption bands of the photoproducts of ruthenium-phenanthroline complexes overlap with the emission spectra of the intact molecules. Forster resonance energy transfer from intact ruthenium complexes to their own photoproducts, generated by singlet oxygen attack of the phenanthroline bridges of the ligands, is suggested to be responsible for the observed decay time effects.