Fullerene internal structure

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-... 

The internal graphitic-like organization of carbon black (CB) particles has been progressively elucidated and we proposed a model illustrated in Figure 6.5, which resulted from the systematic examination at the nanoscale by STM microscope. This model shows scales of carbon graphitic organization and it points out the existence of active sites at the edges. Our recent work reveals the existence of a fullerene-like structure at the surface of the particles ... 

Figure 2.48 The structure of the higher fullerenes. Source Reprinted with permission from Fowler PW, Manolopoulos DE, An Atlas of Fullerenes, International Series of Monographs on Chemistry, Clarendon Press, Oxford, Vol 30, 1995. Copyright 1995, Oxford University Press.

A detailed study of the C60/CNT system (named peapod , Fig. 3.15) was conducted, highlighting how the fullerene appears to be the perfect candidate for encapsulation, as a consequence of the similar graphitic scaffold, an ideal structural match between the C60 spherical shape and the internal CNT channels and strong van der Waals interactions [79]. 

Despite the reduction in symmetry, no additional bands have ever been unambiguously assigned to internal fullerene active vibrations. For multiple addition adducts, the severe disruption to the cage structure results in a markedly different spectrum. 

Igumnov V.S., Carbon nanostructure - an intermediate stage in catalytic conversion of methane // III International Symposium Fullerene and fullerennoid structures in the condensed environments , June, 2004, Minsk. 

Very thin films (monolayer or multilayer) can be studied by IR spectroscopy, provided that the IR beam crosses a reasonably large fraction of the monolayer this can be done by (i) grazing-angle techniques (whereby the IR beam angles of incidence and reflection are of the order of 1° to 3°) or (ii) multiple internal reflections of the IRbeam inside the monolayer (infrared reflectance and absorbance spectroscopy (IRRAS). Fig. 11.19 shows the chemical structure of an analyte (Fullerene-fcz s-[ethylthio-tetrakis(3,4-dibutyT2-thiophene-5-ethenyl)-5-bromo-3,4-dibutyl-2-thiophene] malonate),... 

Olmstead, M.H., de Bettencourt-Dias, A., Duchamp, J.C. etal. (2001) Isolation and structural characterization of the endohedral fullerene Sc2N C-i%. Angewandte Chemie International Edition, 40, 1223-1225. 

Additional very strong confirmation for the geodesic cage structure of fullerenes and the existence of a central metal atom was obtained in a series of shrink wrap experiments showing that the carbon cage bursts a point dictated by the ionic radius of the internal atom. Recent experiments by Freiser and co-workers have verified that externally attached metal atoms do, in fact, behave in a radically different way they react readily and are easily knocked off. 

In addition to the size, also the shape of NMs was shown to play a role in induction of toxicity. NMs made of the same material but in different shapes can be differently internalized into the cells, react with cell membranes, and produce different oxidative effects [6, 14]. Carbon nanomaterials with different geometric structures (single-walled carbon nanotubes [SWCNTs], MWCNTs, and fullerenes) were shown to exhibit quite different cytotoxicity and bioactivity in vitro [15]. The uptake of Au nanospheres and nanorods was also significantly different, illustrating the role of the shape on NM internalization [6, 48],... 

Each Ti bonds to 3C via a bonds and each C bonds to 2Ti and one C. The all-carbon analogue, C20, is not expected to be stable because of severe internal strain (it would be the smallest possible fullerene, p. 280). Note, however, that dodecahedrane, C20H20, is known.An alternative description of the structure (Fig. 8.18b) would be as a weakly bonded cube. Tig, each face of which is capped by a C2 unit. The calculated distances are Ti Ti 302 pm, Ti-C 199 pm and C-C 140 pm (implying some multiple bonding cf. 140 pm in benzene). An alternative Th structure for TigC, which is calculated to have a lower energy, has also been proposed.In this, the Tig array is a tetracapped tetrahedron containing six Ti4 faces in butterfly conformation each of these Ti4 faces can then accommodate a C2 unit as shown in Fig. 8.18c. 

Recently, considerable advances have been made in the production of a different class of nanoscopic carbon structures, namely, carbon nanotubes, which stimulated fundamental research exploring the structure-property relationship of these materials [227]. In their simplest form carbon nanotubes are composed of only a single cylindrieal graphene shell with a central hollow internal cavity. These structurally imiform cylinders are invariably sealed at both ends by bended carbon caps, which contain both five- and six-membered rings similar to the struetures of fullerenes. Based on their similarity with highly graphitized carbonaceous materials, nanotubes have low ehemieal reaetivity. Therefore, the chemistry of earbon nanotubes is mainly focused on opening reaetions at its... 

---