Photophysics and photochemistry of a water-soluble C-60 dendrimer: Fluorescence quenching by halides and photoinduced oxidation of I-

Using electronic absorption spectroscopy, and steady-state and time-resolve d fluorescence, we studied the singlet state properties of dendro[60]fuller ene, a C-60 methanoderivative whose addend is a water-soluble dendrimer. Fl uorescence quenching, especially by halide ions in water, was characterized at several temperatures. From a new relation for the activation energy of a diffusion-influenced reaction and from a comparison with the quenching in organic solvents, it is concluded that the quenching occurs by the externa l heavy-atom effect. An efficient photoinduced oxidation of iodide in aerat ed solutions and in the presence of a fullerene is also reported., The phot oinduced oxidation mechanism exclusively involves ground-state oxygen.