A systematic spectroscopic study of a series of C60 derivatives with different cage functionalizations is reported.
The absorption spectra and absorptivities of the derivatives in solution were measured and compared. By
recording the fluorescence spectra using a near-infrared-sensitive emission spectrometer (extending to 1200
nm), fluorescence quantum yields of the derivatives were determined quantitatively. Fluorescence lifetimes
of the derivatives were obtained using the time-correlated single photon counting technique. The results
show that both fluorescence quantum yields and lifetimes are rather similar for the different classes of C60
derivatives. The nonlinear absorptive properties of the derivatives were evaluated by optical limiting
measurements in solution and in polymer film using the second harmonic of a Q-switched Nd:Yag laser at
532 nm. Effects of different fullerene cage functionalizations on the photophysical properties and optical
limiting responses of the C60 derivatives are discussed.
[60]Fullerene−styrene copolymers with
[60]fullerene contents up to 50% (wt/wt) were
prepared in radical-initiated polymerization reactions. Molecular
weights of different fractions of the
copolymers were determined by gel permeation chromatography
measurements using chloroform and
DMSO as mobile phases. Structures of the copolymers with different
[60]fullerene contents were
characterized by use of proton and 13C NMR, FT-IR, and
thermal analysis methods. The mechanistic
implication of the proposed copolymer structures is
discussed.
The photoreduction of [60]fullerene by triethylamine results in the formation of a cycloadduct N-ethyl-trans-2',5'dimethylpyrrolidino[3',4': 1,21[60lfullerene, which is probably due to sequential intermolecular and intramolecular processes and argues strongly for the presence of ion pairs as intermediates in a room temperature toluene solution.
Fullerene molecules undergo efficient photochemical reactions with tertiary amines to form complex
mixtures of addition products. The separation and identification of several monoadducts from
photochemical reactions of C60 with triethylamine under different experimental conditions are
reported. According to molecular spectroscopic results, the photoaddition of triethylamine to C60 is
initiated via photoinduced electron transfer between the excited singlet C60 and the amine, similar
to photochemical reactions of conventional aromatic molecules with tertiary amines. However, the
reaction products with fullerene are completely different. Mechanistic implications of the results
are discussed.
Mono-and multiple-functionalized C 60 derivatives were synthesized and studied for their photophysical properties. Electronic absorption spectra and absorptivities of the C 60 derivatives in solution were measured and compared. By recording the fluorescence spectra using a near-infrared-sensitive emission spectrometer, we quantitatively determined fluorescence quantum yields of the C 60 derivatives. For the mono-functionalized C 60 derivatives, the compound with a [5,6]-open fulleroid addition pattern on the fullerene cage appeared to be considerably less fluorescent than those with a [6,6]-closed cage addition pattern. Despite the disturbance of the electronic structure via multiple additions to the fullerene cage, the multiple-functionalized C 60 derivatives exhibited no dramatic changes in fluorescence quantum yields in comparison with the mono-functionalized C 60 derivatives. The fluorescence lifetimes of the C 60 derivatives, obtained using the time-correlated single photon-counting technique, were all in the range of 1-3 ns. In addition, the dependencies of the fluorescence intensities and lifetimes of the C 60 derivatives on the concentration of the quencher N,N-diethylaniline (DEA) were evaluated. Apparently, upon photoexcitation, even the C 60 derivatives with a hexa-functionalized fullerene cage underwent significant electron-transfer interactions with the electron donor DEA, resulting in efficient fluorescence quenching. In a polar solvent, the contribution of static quenching also became important. The results for different derivatives and their molecular structural and mechanistic significance are discussed.
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