Chemiluminescence from the Action of Singlet Oxygen (!Ag) on Chlorophyll a and some other Luminescing Substances

In systems containing singlet-oxygen and aromatic fluorescers energy transfer from singletoxygen dimers to the dye should be observable by emission of the fluorescer. In order to prove this hypothesis, externally generated singlet-oxygen (M g) was bubbled through the solutions of dyes (chlorophyll a, eosin y, rhodamine b, luminol, rubrene and acridine orange) in organic solvents. Luminescence could be observed and its spectral distribution analyzed by sharp cut-off filters and interference filters (rubrene). Spectra, rates of oxidation, addition of quenchers and the long lasting time dependence of the reported reactions lead to the conclusion that the observed afterglow is due to chemical oxidation mechanisms producing a chemiluminescence. Therefore an excitation of the substances investigated in these experiments by simple physical energy transfer seems not to be predominant.