Clusters buckyball

Intermediate between the extended four-coordinate connectivities that dominate the low- T solid phase and the two-coordinate ring/chain connectivities that dominate at higher T are certain //jree-coordinate polyhedral structures that retain a degree of cooperative proton ordering. Two examples of such trigonally coordinated buckyball clusters, a 24-mer and a 28-mer, are shown in Fig. 5.31. The... 

Figure 5.31 Water buckyball clusters (with net binding energies in parentheses). (Geometries were optimized at lower 6-31+G (24-mer) or 6-31G (28-mer) basis level, with quoted energetics evaluated at full B3LYP/6-311+ + G" level. Hence, the actual binding energies and H-bond strengths are, if anything, stronger than those quoted in the text.)...

Each vertex of a buckyball cluster is attached by three H-bonds, and hence must have net donor (2D1A) or acceptor (1D2A) character that seems to preclude significant cooperativity. However, by suitably pairing each donor and acceptor monomer, one may produce connected dimers that are each of effective 3D3A pseudo-closed-CT character. Such cooperative dimer units may then be joined in proton-ordered fashion to form closed polyhedra that retain a high degree of cooperative stabilization. 

Figure 5.32 The mixed (H20)23H0C2H5 buckyball cluster (cf. Fig. 5.30(a)), showing the encapsulation of the hydrophobic alkyl group.

V. S. Kuck (eds.), Fullerenes Synthesis, Properties, and Chemistry of Large Carbon Clusters, ACS Symp. Ser. 481, American Chemical Society, Washington, D.C., 1992 H. W. Kroto and D. R. M. Walton (eds.), Fullerenes New Horizons for the Chemistry, Physics, and Astrophysics of Carbon. Cambridge Univ. Press, Cambridge, 1993 H. W. Kroto (ed.), Fullerenes. Pergamon/Elsevier, London, 1993 A. Hirsch, The Chemistry of the Fullerenes. Thieme Verlag, Stuttgart, 1993 H. Aldersley-Williams, The Most Beautiful Molecule Discovery of the Buckyball. Wiley, New York, 1995. 

From a practical point of view, nanotechnology and nanosciences started in the early 1980s. Major developments were the birth of cluster science, the development of the scanning tunneling microscope, the discovery of buck-minsterfullerene (the C60 buckyball) and carbon nanotubes, as well as the synthesis of semiconductor nanocrystals, which led to the development of quantum dots [4]. 

Figure 1. A computer graphic of a buckyball molecule, or carbon cluster, also called a Buckminsterfullerene, named after American engineer Buckminster Fuller.

As stated by Smalley, the name [fullerene] was bom in the dimmest early thinking of how a pure carbon cluster of 60 atoms could eliminate its dangling bonds (Billups and Ciufolini, 1993, foreword vi). In an effort to make clear the shape of the cluster, Smalley asked Kroto the name of the architect who worked with big domes. The answer was Buckminister Fuller. Carbon clusters of all sizes were subsequently named Buckminsterfullerenes, fullerenes, or sometimes buckyballs. A third allotrope of carbon had thus been added to the two (graphite and diamond) already known (see Figure 1). 

Around 1985, Kroto, Smalley, and Curl (Rice University) isolated a molecule of formula Cf,cj from the soot produced by using a laser (or an electric arc) to vaporize graphite. Molecular spectra showed that G , is unusually symmetrical It has only one type of carbon atom by 13C NMR (5143 ppm), and there are only two types of bonds (1.39 A and 1.45 A). Figure 16-16 shows the structure of C(1, which was named buckminsterfiillerene in honor of the American architect R. Buckminster Fuller, whose geodesic domes used similar five- and six-membered rings to form a curved roof. The Cg0 molecules are sometimes called buckyballs, and these types of compounds (Cgo and similar carbon clusters) are called fullerenes. 

In 1985 Kroto and Smolly found the sharply prevailing peaks corresponding to the Ceo and C70 clusters in the mass spectra of graphite vapors. To explain the high stability of Ceo, which they called buckyball, it was assumed that it is a spherical molecule in which atoms are located in the tops of truncated icosahedra [1]. A considerable interest was piqued by buckyball (also known as fullerene) when the method of production of significant amounts of Cgo by electric arch evaporation of graphite in a helium atmosphere had been discovered [2]. 

In addition, since the mid-1980s the chemistry of elemental carbon has flourished. This phenomenon began with the discovery of fullerenes, most notably the cluster Cgo, dubbed buckminsterfullerene after the developer of the geodesic dome. Many other fullerenes (buckyballs) are now known and serve as cores of a variety of derivatives. In... 

Because C50 clusters were so preferentially formed, the group proposed a radically different form of carbon, namely, nearly spherical CgQ molecules. They proposed that the carbon atoms of Cgo form a ball with 32 faces, 12 of them pentagons and 20 hexagons ( FIGURE 12.47), exactly like a soccer ball. The shape of this molecule is reminiscent of the geodesic dome invented by the U.S. engineer and philosopher R. Buckminster Fuller, so Cgo was whimsically named buckminsterfullerene, or buckyball for short. Since the discovery of C q, other related molecules of carbon atoms have been discovered. These molecules are now known as fullerenes. 

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