EXCITED-STATES AND REDUCED AND OXIDIZED FORMS OF C-76(D-2) AND C-78(C-2V')

The singlet and triplet excited state properties of C-76(D-2) and C-78 (C-v') have been investigated using picosecond laser flash photolysis and pulse radiolysis. Both C-76 and C-78 are weakly fluorescent as the y undergo internal nonradiative conversion and intersystem crossing to generate a triplet excited state. Unlike their predecessor, C-60, the excited larger fullerenes have structured spectral bands in the visib le/NIR region. The triplet excited states of C-76 and C-78 were also g enerated independently by energy transfer from triplet excited bipheny l with a diffusion-controlled rate (k(et) approximate to 1 x 10(10) s( -1)). These larger fullerenes readily undergo one-electron reduction a nd oxidation by reacting with radiolytically generated (CH3)(2)C-.(OH) and (CH2Cl2)(.+) radicals. The absorption features of excited states and chemical reactivity of C-76 and C-78 are compared with those of C- 60, C-70, and C-84. The characterization of radical anions of these la rger fullerenes is also made with complementary reduction experiments with UV-irradiated TiO2 nanoparticles.