Chiral fullerene derivatives

A. Classification of Chiral Fullerenes and Chiral Fullerene Derivatives... 

Depending on the origin of their chirality, three classes of chiral fullerene derivatives can be distinguished (Figure l.l) 22 25... 

Further explorations should be done in the stereoselective synthesis of chiral fullerene derivatives, a field initiated by the kinetic resolution of D2-C through diastereoselective osmylation with 0s04 in the presence of alkaloid-derived ligands. Besides, a few diastereoselective macrocyclizations by bridging of C6o with enantiomerically pure, bifunctional reagents have been achieved with high d.e. s. The use of optically pure fullerene derivatives as bulky chiral auxiliaries... 

A proposed structural description of chiral fullerene derivatives using a bond-labeling algorithm eventually also relies on the helicity of the fullerene numbering schemes.110... 

According to structural criteria of chiral fullerene derivatives, three different types of core functionalization patterns can be distinguished [34] (Fig. 2) ... 

Only one year after fullerenes Cgo and C70 became available in multigram amounts, the first chiral carbon cage Cj -D2 was chromatographically isolated from fullerene soot extract [47]. Since then, a large number of chiral fullerene derivatives have been obtained [48] and classified on the base of their chirality as follows ... 

Also, chiral fullerene derivatives have found use in biological applications [50] and in polymer science as helicity inducers [51]. Recently, fullerene chirality has demonstrated to be critical in generating a supramolecular architecture of donor-acceptor dyads (based in a chiral pyrrolidino[60]fullerene) giving rise to photoconductive nanofibers displaying very high ambipolar charge-carrier mobility ( 10 cm /(V s)), which was higher than that obtained from racemic dyads in spherical assembly [52]. 

Fig. 2. By rolling up a graphene sheet (a single layer of ear-bon atoms from a 3D graphite erystal) as a cylinder and capping each end of the eyiinder with half of a fullerene molecule, a fullerene-derived tubule, one layer in thickness, is formed. Shown here is a schematic theoretical model for a single-wall carbon tubule with the tubule axis OB (see Fig. 1) normal to (a) the 6 = 30° direction (an armchair tubule), (b) the 6 = 0° direction (a zigzag tubule), and (c) a general direction B with 0 < 6 < 30° (a chiral tubule). The actual tubules shown in the figure correspond to (n,m) values of (a) (5,5), (b) (9,0), and (c) (10,5).

A review9 with more than 37 references includes an examination of symmetry groups and chirality conditions for C60 and C70 bonded to one or two metals in rf and/or rf fashion. Palladium and platinum rf complexes of C6o and C70 are described (novel synthesis, NMR spectra, electrochemistry) as well as first optically active organometallic fullerene derivatives. 

Herrmann A, Ruettimann M, Thilgen C, Diederich F (1995) Multiple cyclopropanations of C70. Synthesis and characterization of bis-, tris-, and tetrakis-adducts and chiroptical properties of bis-adducts with chiral addends, including a recommendation for the configurational description of fullerene derivatives with a chiral addition pattern. Helv. Chim. Acta 78 1673-1704. 

Regarding the plan of the chapter, we should mention that the discussion of individual molecules (generally represented in the figures by a single enantiomer) mostly follows the classification of fullerene derivatives according to different types of chirality (cf. Section II.A). For reasons of comprehension, however, we present certain chemically related compounds together even if they belong to different classes. 

II. CONFIGURATIONAL DESCRIPTION OF CHIRAL FULLERENES AND FULLERENE DERIVATIVES WITH A CHIRAL FUNCTIONALIZATION PATTERN... 

Figure 1.1. Elow diagram for the facile classification of different types of fullerene-spheroid chirality in fullerene derivatives.

A. Fullerene Derivatives with an Inherently Chiral Addition Pattern... 

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