Elongated fullerenes

Elongated fullerenes, 12 232 Elongation, of olefin fibers, 11 226 Elongational rheometer, 21 740 Elongation at break, 10 177 19 743 Elongation viscosity, of olefin fibers, 11 233, 234... 

Fig. 1. Representation of a nanotube, which can be regarded as an elongated fullerene...

In addition to chemical or physical properties, a fascinating aspect of fullerene related materials is their central empty space, where atoms, molecules or particles can be enclosed. The enclosed particles are then protected by the robust graphitic layers from chemical or mechanical effects. The very long cavities of CNTs have a special potential due to their high aspect ratio and they can be used as templates to fabricate elongated nanostructures. 

As a third group of fullerene-like systems whose synthetic development is identified as a major future challenge are structurally defined single-walled carbon nanotubes (SWNTs) with uniform helicity and length, including their covalent and non-covalent derivatives. SWNTs can be considered as elongated giant fullerenes. 

Self-assembled objects of various nature bear the name nanotubes. Some of them are covalently bound structures while other are self-assembled aggregates.The best known among them are probably elongated fullerenoid structures called carbon nanotubes obtained, in addition to spheroidal fullerenes,... 

As far as the fullerene internal structure is concerned, there is little change on metal complexation. The metal bound transannular [6,6] bond is elongated relative to the remaining fullerene C=C bonds. It often attains a length (=1.5 A) comparable with that of other C—C bonds such as the transannular [6,5] bond or those for an analogous alkene complex. The structure often is described as metallacyclopro-... 

One of the clearest cases is obtained for a salt of bis(triphenylphosphine)-iminium ion (PPN+) and Cf(0. It was found [10] that the distorted fullerene molecule exhibits, as can be seen in Fig. 4, an axial elongation with a rhombic squash, in good agreement with the type of JTD described previously. While in the ideal icosahedral structure the distances of the carbon atoms from the center of the molecule are exactly equal, in the distorted structure there is a spread of 0.04 A around the mean value of 3.542 A. 

The term zeppelene (Figure 10) has been coined to describe the discrete molecules formed by closing single cylinders at both ends (or alternatively by elongating a fullerene). The nonplanar nature of all these materials has opened a debate on the relative stabilities of carbon structures on the microscopic and macroscopic scale, and has consequences for the generally accepted planar 2D description of graphite. ... 

The d electron density of the metal can donate to an empty antibonding orbital of a fullerene. This pulls the two carbons involved slightly away from the Cgo surface. In addition, the distance between these carbons is elongated slightly as a consequence of this interaction, which populates an orbital that is antibonding with respect to the C C bond. This increase in C—C bond distance is analogous to the elongation that occurs when ethylene and other alkenes bond to metals, as discussed in Section 13-5-1. 

Finally, we note that there is much interest in so-called nanotubes made of C atoms. These appear to be essentially elongated giant fullerenes [676]. 

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