Chiral fullerene derivatives structures

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) ... 

I>2-C76, >3-C78, and D2-Cu are the inherently chiral higher fullerenes of which defined derivatives have been isolated and in part structurally characterized.17,60 As a consequence of their inherent chirality, all derivatives of these fullerenes are chiral, except for as yet unknown me so type combinations of both optical antipodes of a given constitution. 

Several groups have noted similar findings for azide addition, in which the structure of the bisadduct depends on the nature of the starting alkyl azide or bisazide [39-41]. Even chiral bisazafulleroids have been prepared [42,43]. As an interesting example, it was found that subsequent addition of azido ester to N-ethoxycarbonyl-azirenofullerene resulted in the formation of bisadduct 12 and not 11 [40]. Structure 12 constitutes the first fullerene derivative having [6,... 

The fullerene derivatives at the focus of the present review result from exohedral addition to the larger carbon spheroids [27] with particular emphasis being given to the structural aspects related to chirality. However, a number of other higher fullerene derivatives, including chiral structures as well, is worth being briefly mentioned. 

This volume, which complements the earlier one, contains 9 chapters written by experts from 7 countries. These include a chapter on the dynamic behavior of organolithium compounds, written by one of the pioneers in the field, and a specific chapter on the structure and dynamics of chiral lithium amides in particular. The use of such amides in asymmetric synthesis is covered in another chapter, and other synthetic aspects are covered in chapters on acyllithium derivatives, on the carbolithiation reaction and on organolithi-ums as synthetic intermediates for tandem reactions. Other topics include the chemistry of ketone dilithio compounds, the chemistry of lithium enolates and homoenolates, and polycyclic and fullerene lithium carbanions. 

Carbon nanotubes (CNTs) are members of the Fullerene structural family. Their name is derived from their long, hollow structure with the walls formed by one-atom-thick sheets of carbon, called graphene (Fig. 3.8). The manner in which these sheets are connected to form tubes at specific and discrete ( chiral ) angles and the combination of the angle and radius decides the nanotube properties for example, whether the individual nanotube exhibits metal or semiconductor like behaviour. The values of n and m are used not only for the chirality or twist but also to draw a line between metallic and semiconducting nanotubes. In other words, chirality in turn affects the conductance, density, lattice structure, and certain other properties of the nanotube. A nanotube is considered metallic if the value m is divisible by three. Otherwise, the nanotube is semiconducting. 

Other cyclophanes sharing this motif have also been realized, such as compounds 70-71 and 72-76, synthesized by the groups of Rubin [29] and Tobe [30], respectively. While crystallographic analysis was not performed on any of these derivatives, it is reasonable to assume that due to stmctural similarities to cyclophane 69, they would also adopt helically chiral conformations. As with compound 69, the three-dimensional cage compounds 70-71 and 72-75 were targeted as precursors to fullerene and diazafullerene structures [31]. The most recent members to join this class of compounds are the cyclophanes 76, introduced by Tobe and coworkers as a precursor to C78 fullerene [32]. 

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