Quantitative spectroscopic studies of the photoexcited state properties of methano- and pyrrolidino-[60]fullerene derivatives

UV/vis absorption and fluorescence spectra and fluorescence quantum yields and lifetimes of a series of methano- and pyrrolidino-[60]fullerene derivatives in different solvents are studied systematically. The absorption and fluorescence properties of the derivatives with different substituents are somewhat different from those of [60]fullerene, but very similar among themselves, indicating that the low-lying transitions and the photoexcited state processes are dictated by the electronic structures of functionalized [60]fullerene cages. The results also allow an examination of the issue concerning discrepancies between experimentally determined transition probabilities and those calculated in terms of the Strickler-Berg equation for fullerene molecules. In addition, quenchings of the excited singlet states of the [60]fullerene derivatives by electron donor N,N-diethylaniline (DEA) and the formation of emissive fullerene-DEA exciplexes in solvents of different polarities are investigated.