Fullerene cations derivatized

Derivatized fullerene cations, such as RCso and RC7o, are formally produced by adding a cationic species R+ to an sp hybridized carbon of a fullerene core. Cations with additional attached groups, such as R Cgo n odd number) are also conceivable. Unlike radical cations, these cations are carbenium ions (trivalent carbo-cations) and have no unpaired electrons. Besides the addition of R to C o (method (a)), four other methods ((b)-(e)), shown in Scheme 9.2, are currently known for the generation of RCeo. As described in the following sections, these approaches have been successfully employed to produce the derivatized Ceo and C70 cations, either as long-lived species or as reactive intermediates. 

Reaction of 175 with Cgg yields a hydroxy-functionalized fullerene that can be further derivatized. This hydroxy-fullerene was coupled with a porphyrine unit via a polyethyleneglycol-Hnker. This linker can be arranged similarly to a crown-ether to complex metal cations. Complexation is used to tune the distance between the porphyrin imit and the Cgg-moiety and thus tune the donor-acceptor properties of this porphyrin-fuUerene hybrid [177]. 

The parent oxacalix[3] arenas show little ability to bind alkali metals,however, a range of quaternary ammonium cations are attracted to the symmetric cavity. Deprotonation of the phenol moieties allows them to bind to transition metals (scandium, titanium, vanadium, rhodium, molybdenum, gold, etc.), lanthanides (lutetium. yttrium, and lanthanum), and actinides (uranium as uranyl). Oxacalix[3]arenes derivatized on the lower rim can complex gallium, mercury, and alkali metals, including sodium, in a manner reminiscent of natural transmembrane cation filters. One major use was to purify crude samples of fullerenes. The pseudo-Cs symmetry of the macrocyclic cavity is complementary to threefold symmetry elements of Cgo. which binds preferentially in... 

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