Photophysical and photochemical properties of C120O, a C60 dimer linked by a saturated furan ring, have been characterized by various time-resolved spectroscopic methods. A steady-state absorption band of C120O is blue-shifted compared with those of 1,2-adducts of C60 (C60R). The fluorescence lifetime and quantum yield were estimated to be 1.7 ns and 8.7 × 10-4, respectively, which are similar to those of C60R and C120. On the other hand, the lifetime of the triplet excited state (3C120O*) was estimated to be 0.16 μs, which is quite shorter than those of C60 (55 μs), C60R (24-29 μs), and C120 (23 μs). Furthermore, the quantum yield for the intersystem crossing process was as low as 0.48. These unusual triplet properties of 3C120O* indicate that the triplet excited C60 moiety in 3C120O* was influenced by an adjacent π-electron system of another C60 moiety in the ground state. Ground-state reduction of C120O was observed in the reaction with tetrakis-(dimethylamino)ethylene, indicating the stable radical anion formation of C120O, in contrast to the unstable radical anion of C120. Photoinduced electron transfer from 1,4-diazabicyclo[2.2.2]octane to 3C120O* was confirmed by an observation of the transient absorption band of the radical anion of C120O in the near-IR region. Oxidation of C120O was also performed by employing a cosensitization method. The reaction rate constants of the both photoinduced reduction and oxidation were slightly smaller than those of C60 and C60R.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry