Molecules of C60 covalently connected with N-ethylcarbazole (EtCz) and triphenylamine (TPA) have been synthesized. Photoinduced electron transfer in C60-EtCz and C60-TPA has been studied in polar and nonpolar solvents using time-resolved transient absorption and fluorescence measurements. From the fluorescence lifetimes, the excited singlet state of the C60 moiety (1C*60) of C60-TPA generates predominantly C60̇- - TPȦ+, which decays quickly to the ground state within 6 ns even in polar solvents. In the case of C60-EtCz, on the other hand, about half of the 1C*60 moiety generates short-lived C 60̇--EtCż_, while the other half of the 1C*60 moiety is transferred to the 3C*60 moiety via intersystem crossing in dimethylformamide, in which the energy level of C60 ̇--EtCż+ is lower than that of 3C*60. Thus, the charge separation takes place via 3C*60 generating C60̇-- EtCż+, having a lifetime as long as 300 ns, probably because of the triplet spin character of C60̇--EtCz ̇+. A special property of the EtCz moiety to stabilize the hole in the charge-separated state was revealed.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry