Photochemistry and photophysics of the new C_(120)O_2 isomer formed by dimerization of 5,6-C_(60)O

摘要

A new isomer of dimeric C_(60) oxides has been synthesized and its photophysical and photochemical properties have been investigated. The new dimer is formed with very high yield by the room temperature dimerization of a recently discovered isomer of C_(60)O, the [5,6]-open oxidoannulene. Excited singlet- and triplet-state properties of the C_(120)O_2 product have been characterized by various spectroscopic techniques and compared to those of C_(120), the [2+2]-dimer of C_(60). The ground state absorption spectrum of C_(120)O_2 in toluene is slightly red-shifted relative to that of C_(120), which a distinctive peak at 329 nm and an S_1-S_0 origin band at 704 nm. Its fluorescence spectrum shows two major peaks at 718 and 793 nm. In room temperature toluene, the measured triplet state intrinsic lifetime of this compound is 34 ± 2 μs, a value somewhat shorter than that of C_(120) (44 μs). It is also found that C_(120)O_2 undergoes photodissociation (through T_) to regenerate its precursor, [5,6]-open C_(60)O. This oxidoannulene can thus be converted to C_(120)C_2 by thermal self-reaction and then restored to monomeric [5,6]-C_(60)O by photolysis.