Fullerene acceptors/derivatives synthesis

As mentioned previously, photocycloaddition reactions are a useful method for obtaining fullerene derivatives fused directly to heterocycles. Such compounds have attracted much interest because they might have interesting properties, e.g., amino acid fullerene derivatives as biologically active compounds or pyrrolidino-fullerenes as key precursors for a great number of fullerenes donor-acceptor bridged dyads and triads. Fullerenes functionalized with silicon compounds are of great interest in materials science. The synthesis of these compounds will be described in this section. 

Investigations concerning the synthesis and electrochemical behavior of a new class of acceptor-substituted isoxazolofullerenes have been reported. In this instance, such fullerene derivatives were synthesized by Suzuki coupling (Eq. (89)) [142]. 

Langa, who has reported several C o derivatives with intramolecular PET processes, recently described the synthesis under microwave irradiation conditions of two pyrazolino [60]fullerene (58a,b) bearing electron-withdrawing substituents. The resulting fullerene derivatives were highly soluble in several polar and nonpolar solvents, and electrochemical studies revealed improved electron-acceptor properties compared with unmodified Ceo [63]. 

Cyclopentadienyl rings substituted by fullerene units have been synthesized in order to obtain molecules presenting donor-acceptor interactions.The synthesis involves the [4- -2]-cycloaddition of a CoCp(C4Ph4) derivative with Cso at rather high temperatures that led to an organocobalt compound 314 stable in air but which proved to be apparently unstable under redox conditions (Equation (49)). 

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