Fullerenes CORE structures

The soccer ball shaped framework of Cgg was confirmed for the first time by the X-ray crystal structure of 13 [52]. The bridging of the OSO4 unit occurs in the characteristic 1,2-mode to a [6,6] double bond of the fullerene core. The 17 sets of carbons in the C2v-symmetric 13 were assigned using the 2D NMR INADEQUATE technique on the basis of their connectivities [53]. In these experiments C-enriched material was used. The coupling constants fall into three categories, 48, 54—57 and 65-71 Hz. These values can be attributed to the three types of C-C bonds present in 13, namely C(sp )-C(sp ), the longer [5,6], and the shorter [6,6] bonds, respectively [53]. 

The last group of dyads considered here are those that incorporate TTFs in their structure. TTFs are powerful organic donors, which, when linked to the fullerene core and engaged in charge-separation processes, gain rather than lose aromaticity [128]. The modification of the donor strength on the TTF moiety in dyads (31a-c) allows the tuning of the... 

In comparison with pristine C6o and C70, the fullerene derivatives (Fig. 2) show partly different photophysical properties due to the pertubation of the fullerene s TT-electron system. The degree of variation is dependent on (1) the electronic structure of the functionalizing group, (2) the number of addends, and (3) in the case of multiple adducts on the addition pattern at the fullerene core [59-112],... 

Photoinduced electron transfer from the amine to the fullerene core leading to a radical ion pair is suggested to be the initial step in the reaction mechanism (Scheme 39). Formation of the bis-[6,6] closed adduct proceeds via [3 + 2] cycloaddition of the tertiary amine followed by a [2 + 2] cycloaddition of the vinyl group and the C6o double bond adjacent to the previously formed ring connection leading to a structure analogous to 1,2,3,4-C6oH4-... 

Viable means of overcoming the insolubility of pristine fullerenes in polar solvents involve (i) incorporation of pristine fullerenes into the hydrophobic cavity of water-soluble host structures (e.g. cyclodextrin [77, 78], surfactants [79-82], and vesicles [81, 83, 84], or (ii) functionalization of the fullerene core with hydrophilic addends (e.g. C6oC(COO-)2, C60 [C(0CH2CH2)3CH3]2, C6o(C4HioN+), etc.) [2]... 

Micellar aggregation of the C6oC(COO )2 derivative in water, a consequence of its amphiphilic structure (i.e., hydrophobic fullerene core and hydrophilic carbox-ylates), is responsible for the lack of reduction [89, 90], These clusters are considered to contain an inward oriented hydrophobic fullerene moiety and a hydrophilic layer of carboxylate head groups, which prevent the negatively charged electrons from approaching the fullerene core. 

Several studies have demonstrated the successful incorporation of [60]fullerene into polymeric structures by following two general concepts (i) in-chain addition, so called pearl necklace type polymers or (ii) on-chain addition pendant polymers. Pendant copolymers emerge predominantly from the controlled mono- and multiple functionalization of the fullerene core with different amine-, azide-, ethylene propylene terpolymer, polystyrene, poly(oxyethylene) and poly(oxypropylene) precursors [63.64.65.66.67 and 68]. On the other hand, (-CggPd-) polymers of the pearl necklace type were formed via the periodic linkage of [60]fullerene and Pd monomer units after their initial reaction with the/ -xylylene diradical [69,70 and 71]. 

In summary, incorporation of [60]flillerene into artificial bilayer membranes, despite being successful in principle, nevertheless, disclosed a number of unexpected complications. The most dominant parameter, in this view, is the strong aggregation forces among the fullerene cores. The lack of appropriately structured domains within the vesicular hosts, which could assist in keeping the fullerene units apart, is believed to be the reason for the instaneous cluster formation. The incorporation of a number of suitably functionalized derivatives, which on their own bear hydrophobic and hydrophilic substructures, will be discussed further below. 

In conclusion, structurally balanced fullerene derivatives were successfully incorporated into various vesicular matrices. Truly monomeric immersion of amphiphilic C6o(C4HioN ) and C6o[C(OCH2CH2)3CH3]2 derivatives into the polar head group anchored the fullerene core still close enough to the lipid bilayer interface to facilitate very efficient reductions by hydrated electrons and CH2OH radicals. 

The reactivity of Qo comparable to that of electron deficient conjugated olefins is nicely reflected by reactions with transition metal complexes. A variety of single crystal structures and spectroscopic studies show that the complexation of transition metals to the fullerene core proceeds in a dihapto manner or as hydrometalation reactions rather than in rf- or ] -binding mode. This was elegantly demonstrated by the reaction of Cgg with ruthenium complexes (Scheme 8) [144]. A variety of iridium complexes ( ] -Cgo)Ir(CO)Cl(PR R R )2 were synthesized by allowing Cgg to react with different Vaska-type complexes Ir(CO)Cl(PR R R )2 [145]. ] -Complex formation was also observed upon reaction of Cgo with other Ir [146] as well as Rh [147] complexes. Hydro-metallation was obtained with Cp2Zr(H)Cl [140]. 

The construction of well-ordered structures composed of fullerene derivatives not only in the bulk, but also on the surface is essential for the creation of a variety of different functional devices. Fullerene, however, is spherical in shape, and tends to form aggregates, which makes it difficult to construct well-ordered structures. This chapter will focus on the assembly of fullerene derivatives to form 1-D, 2-D, and 3-D organization structures in both the solid state and on the surface. Particular emphasis will be given to descriptions of the liquid crystals and self-assembled monolayers (SAMs) of fullerene derivatives with five feathers or legs attached to the fullerene core, as well as the columnar fullerene alignment triggered by thermal crystallization. During the development of... 

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