Photoinduced quenching of the luminescence of singlet oxygen in fullerene solutions

The photoinduced quenching of the luminescence of singlet oxygen in solutions of C-60 and C-70 fullerenes in CCl4 is studied. It is shown that intense pumping of the solutions by ultraviolet and visible radiation leads to formation of relatively long-lived fullerene-oxygen complexes, which are effective quenchers of the (1)Delta(g) excited state of singlet oxygen. The behavior of these complexes depending on the experimental conditions (pumping intensity, concentration of fullerenes in the solution, and temperature) is studied. Decomposition of complexes with time is investigated. It is shown that, upon formation and gradual degradation of these complexes, the absorption spectra of the solutions change with time. The C-60 fullerene is shown to be more stable to the intense pumping, its concentration being completely restored with the decomposition of the complexes. At the same time, C-70 fullerene is partly irreversibly lost and the solution does not reach its initial concentration after decomposition of complexes.