FLUORESCENCE OF FULLERENE-C-70 AND ITS QUENCHING BY LONG-RANGE INTERMOLECULAR ELECTRON-TRANSFER

The fluorescence spectrum and fluorescence quantum yield of C70 were determined in a number of solvents at room temperature. A well resolved fluorescence excitation spectrum, which matches the absorption spectrum, was obtained over a broad wavelength region (250 to 580 nm. in n-hexane). The fluorescence lifetime (627 ps in benzene) was determined, thereby settling the uncertainty about the singlet lifetime Of C70. It is shown that the quenching of the fluorescence by organic electron donors involves both dynamic and static mechanisms. The contribution of the latter is much more pronounced than can be explained from the degree of ground-state charge transfer complexation. Analysis in terms of a Perrin model indicates that long-range intermolecular electron transfer is important, with a radius of action that increases sharply when the donor oxidation potential is lowered.