Oxidation fullerenes

A final noteworthy study [79] is that of CgoHj. When is reduced by bulk electrolysis, two superimposed spectra, each exhibiting a single line, are observed. These were assigned to and C. Since most of the spectra recorded for fullerene ions exhibit only a single line, there is much that remains to be done in the future to understand better the various fullerene oxidation states. 

V [10], Toluene is oxidized at higher potentials (1.98-2.3 V) [19]. However when the solution contains more readily anode-oxidizable components, such as ethanol and fullerene, oxidation products can react with toluene present in the solvate shell of the combined donor-acceptor complex. 

A fullerene oxide, CeoO, has been prepared by photo-irradiating an oxygenated benzene solution of... 

Excellent separation can be achieved by using silica with bonded octadecylsilyl groups and optimized composition of alcohol - hydrocarbon eluent [16]. At separation of Ceo and C70 on fj. Bondapak 10 C18 from mobile phase containing 70% of n-hexane and 30% of isopropanol the selectivity was 1.91 (Fig. 3 a.). For the detection UV detector at 254 nm can be used. In this case the oxide of Ceo can be separated from Ceo with the selectivity 1.18 and the oxide is eluted before Ceo owing to more strong interaction of Ceo oxide with alcohol in eluent. The determination of fullerene oxides is quite important in analysis of the purity of fullerenes. 

For the purification of fullerenes from the fullerene oxides the activated alumina and silica can be used. Fulllerene oxides are adsorbed strongly on such adsorbents from solution and the oxides are removed from fullerene samples. For the preparative separation of fullerenes at present activated carbons and graphite are used [11-14], For this purpose silica with the deposited carbon layer [16] can be used also. In this case it is very easily to regulate the pore diameter and specific surface area of adsorbents as well as particle diameter. Such adsorbents is very important for the decreasing of fullerenes loss. On preparative separation of fullerenes on LiChrosorb SI 60 with deposited carbon layer by modified method [15] on glass column first fractions contained quite pure Csq. 

Oxidation The radiation-chemically induced ionization of chlorinated hydrocarbons, i.e., dichloroethane (DCE) leads to the initial generation of the corresponding solvent radical cation, [DCE] ". The electron affinity of the latter is sufficient to oxidize the fullerene moiety ([60]fullerene E1/2 = +1.26 versus Fc / Fc ). Pulse radiolytic experiments with [60]fullerene in nitrogen-saturated or aerated DCM solutions yielded a doublet with maxima at 960 and 980 nm (Figure 1) (12-18). This fingerprint is identical to that detected in photolytic oxidation experiments and that computed in CNDO/S calculations. Rate constants for the [60]fullerene oxidation are typically very fast with estimated values IC7 > 2 x 10 ° M s. The 7t-radical cation is short-lived and decays via a concentration-dependent bimolecular dimerization reaction with a ground state molecule (kg = 6 x lO M s ) (13). 

In analogy to the fullerene oxidation, the arene radical cations were generated in deoxygenated DCM solutions containing ca. 2 x 10 M of the respective arenes. As a convenient means to probe the formation and the lifetime of the generated (arene)" the respective absorptions in the UV-VIS region were monitored. 

Fullerene oxide 4 in the presence of an excess of a Lewis acid reacts with toluene to afford l,4-bis-(p-tolyl)-l,4-dihydro[60]fullerene 9. Upon increasing the steric hindrance of the aromatic reagent, the intermediate compound 8 can be isolated in appreciable yield (060L3203). 

Hydroxylated fullerene Oxidative eukaryotic cell damage... 

Scheme 3.5 Synthesis of l,4-di(aryl)[60]fullerenes. (a) Starting from fullerene oxide, (b) Reaction with arylhydrazine. (c) Friedel-Crafts type reaction. (d) Rhodium-catalyzed monoarylation.

SCHEME 32 Photolysis of C O, leading to the [5,6] open fullerene oxide 76 (oxidoannulene). 

The synthesis of fullerene epoxides via [2 -I- l]-photoq cloaddition of singlet oxygen has already been discussed (in the section [2 -1- l]-Photocycloaddition ). Alternatively, fullerene oxides can also be obtained by thermolysis or photolysis of the [6,6]-closed ozone adduct of Qq and C70, namely 60 3 75 and C70O3 77.Thermolysis of QqOj yields the fullerene epoxide with a [6,6]-closed structure. In contrast, photolysis resulted in the formation of the [5,6]-open oxidoannulene 76 with an ether structure (Scheme 32). 

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