Fullerenes ligands

One of the most fascinating developments in modem chemistry has been the synthesis of buckminsterfullerene, C60, and the related fullerenes ( buckyballs ) with their geodesic dome-like shapes. First reported as synthesized in the gas phase 

46The structure of C60 has the same symmetry characteristics as an icosahedron. 

This is indicative of a greater degree of n bonding at the fusion of the 6-membered rings. 

A common route to the synthesis of fullerene complexes is by displacement of other ligands, typically those weakly coordinated to metals. Examples of such ligands include ethylene (equation 6.14) and CH3CN (equation 6.15). 

49For a recent review of fullerene complexes, see A. Hirsch and M. Brettreich, Fullerenes, Wiley-VCH Weinheim, Germany, 2005, pp. 231-250. 

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Figure 28 shows the molecular structure of [Fe2( -S)2(772-C60)(CO)6], in which again there is no direct bond between the metal(s) and the fullerene ligand.40... 

The two effects can add or compensate each other. In this way, the measurement of the shift in redox potentials through electrochemical techniques offers a simple, but powerful tool to evaluate the overall electronic factors governing the interaction of the metal fragments with the fullerene ligands. 

Fig. 11.3. A representative synthetic barrel-stave pore self-assembled from four p-octiphenyl monomers (left). Molecular model with p-octiphenyl staves in grey, j -sheet hoops in yellow, external fullerene ligands in gold and an internal a-helix blocker in red (right, adapted from Ref. 4).

There are two types of C=C double bonds in the fullerene ligand, C j those that lie at the junction of two six-membered rings and those that lie at the junction of a five-membered ring with a six-membered ring. Taking into consideration the different curvature of the fullerene at these two different ring junctions, predict at which type of junction the compound [(PPh3)jPt( -C (,)] will bond. Explain your answer. 

A first demonstration was presented in form of a ZriP-pyridine-Ceo complex. In the latter the reversible coordination of a pyridine functionalized fullerene ligand (pyridine-Ceo) to the square-planar zine center constitutes a labile, but nevertheless measurable, (K 5,000 M" ) binding motif, explored by three different research teams... 

Rhodium 77 -eomplexes bearing an indenyl-type fullerene ligand, RhtCeotPhCHzIzPhKcod), Rh C6o(PhCH2)2Ph (nbd), and Rh(C7oPh3)(cod), were synthesized from the corresponding fullerene tri-adduets (Scheme 52). ... 

Armspach D, Constable E C, Diederich F, Housecraft C E and Nierengarten J-F 1996 Bucky-ligands fullerene-substituted oligopyridines for metallosupramolecular chemistry J. Chem. Soc., Chem. Commun. 2009-10... 

The following is a comprehensive smwey of the chemistry of macrocycles comprised entirely of phenyl and acetylenic moieties. Although over fom" decades old, this area of research has come into its own just in the last few years. Widespread interest in the field has been spurred by recent discoveries utilizing these compoimds as ligands for organometallic chemistry, hosts for binding guest molecules, models of synthetic carbon allotropes, and precursors to fullerenes and other carbon-rich materials. This review will discuss the preparation of a tremendous variety of novel structm-es and detail the development of versatile synthetic methods for macro cycle construction. 

The elution of [60]- and [70]fullerenes was measured in water-methanol as a function of temperature on a poly(octadecylsiloxane) phase.67 The retention was shown to be dependent on the surface tension of the stationary phase through a simple geometrical model in which the solute formed a cavity in the stationary phase. In affinity chromatography, it was demonstrated that low ligand density may be a requirement for specificity of binding.68... 

The following sections discuss many of the major particle types and provide bioconjugation options for the coupling of ligands to the surface of functionalized particles. Some additional nanoparticle constructs, including gold particles, dendrimers, carbon nanotubes, Buckyballs and fullerenes, and quantum dots are discussed more fully elsewhere (see Chapter 7 Chapter 9, Section 10 Chapter 15 and Chapter 24). 

The PCBM methyl ester can be used for coupling amine-containing ligands after removal of the methyl group and activation of the carboxylate using a number of different reaction strategies. Hummelen et al. (1995) successfully coupled cholestanol and histamine to the fuller-ene-PCBM derivative (after acid chloride formation) for use in fabrication of photodetectors and biological studies, respectively. For specific applications of PCBM-fullerenes, see Shaheen et al. (2001), Brabec et al. (2001), Yu et al. (1995), Mecher et al. (2002), Meijer et al. (2003), van Duren et al. (2004), and Anthopoulos et al. (2004). 

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