Fullerenes cyclotriveratrylene

Figure 10 Regioselective one-step synthesis of topologically chiral trans-3,trans-3,trans-3 and e,e,e [60]fullerene-cyclotriveratrylene tris-adducts.

In principle, there are four basic strategies to compensate for the repulsive effects between the hydrophobic fullerene surface and water (a) encapsulation in the internal hydrophobic moiety of water-soluble hosts like cyclodextrins (Andersson et al., 1992 Murthy and Geckeler, 2001), calixarenes (Kunsagi-Mate et al., 2004) or cyclotriveratrylenes (Rio and Nierengarten, 2002) (b) supramolecular or covalent incorporation of fullerenes or derivatives into water-soluble polymers (Giacalone and Martin, 2006) or biomolecules like proteins (Pellarini et al., 2001 Yang et al., 2007) (c) suspension with the aid of appropriate surfactants and (d) direct exohe-dral functionalization in order to introduce hydrophilic moieties. 

Rio Y, Nierengarten J-F (2002) Water soluble supramolecular cyclotriveratrylene-[60]fullerene complexes with potential for biological applications. Tetrahedron Lett. 43 4321 4324. 

Cyclotriveratrylene synthesis is a poorly understood process, as with many reactions between phenols and aldehydes, and yields are as variable as the methods to prepare them a review lists fifteen different conditions that give between 21 and 89% yield. Despite this the compounds are worth preparing as they have an interesting affinity for buckminsterfullerene, C6o, and are cited in papers and patents that describe methods to isolate pure C6o from a mixture of fullerenes [50], It transpires that the threefold symmetry of cyclotriveratrylene is complementary to the threefold axis of C6o and that the two form very stable complexes in toluene as shown in Fig. 1.12, which precipitate leaving other fullerenes in solution. If the precipitate is isolated and taken up in chloroform the complex dissociates leaving cyclotriveratrylene in solution and precipitates C6o- The purity of the C6o treated in this way is significantly enriched and can approach 100%. At the time of this discovery fullerene research was very much in its infancy, and the material available was of variable purity, making the purification technique an important milestone in the history of fullerene chemistry. 

This experiment forms the basis of the patented process [8] to separate Cgo from higher fullerenes using a wide range of macrocycles with threefold symmetry, such as cyclotriveratrylene, 4-f-butylcalix[6]arene or 4-benzyloxacalix[3]arene, or fivefold symmetry, as in the case of 4-benzylcalix[5]arene. 

An interesting example of the interplay between solid-state clathrands and solution-phase cavitands is provided by cyclotriveratrylene (CTV, 8). In the solid state, the saucer-shaped CTV molecules stack one on top of another in the two most common phases (x and and hence, while the molecules possess shallow molecular cavities, they do not include guests such as solvent molecules, which instead are located in voids between host stacks. However, larger guests such as buckminsterfuller-ene C6o, organometallic sandwich compounds,or carboranes form intracavity inclusion compounds, and the association persists in the solid state, with potential applications, for example, in the selective purification of fullerenes. Thus, CTV is both a cavitand and a clathrand. The cavitand behavior of CTV is highlighted by the chemistry of the double-CTV cryptophanes that form very stable solution complexes with a variety of halocarbon guests. 

The number of papers reporting the role of CH/ti interaction is rapidly increasing. Only recent key papers are cited here. Chloroform interacts favorably with an arene n-oloud of fullerene complexes of calixarenes " and cyclotriveratrylene. Evidence for the role of CH/ti interaction in self-assembly was presented.The significance in molecular capsules " " and lattice- and cavity-inclusion type clathrates is well documented. 

Matching the convex shape of Ceo to a concave siuface has been used to gain control over the inherently weak association between a host moiety and a molecular guest. A built-in shape- and size-specific receptor site ensures efficient binding, but it also exerts a major challenge to find the right match. The following examples form remarkably stable composites with fullerenes nano-sized, bowl-shaped molecules or container molecules with curved, open-ended cavities, such as cyclodextrins, benzotri(benzonorbomadienes), calixarenes, calixnaphthalenes and cyclotriveratrylene. ... 

Matsubara, H. et al. Supramolecular inclusion complexes of fullerenes using cyclotriveratrylene derivatives with aromatic pendants. Chem. Lett. 27, 923-924,1998. 

There are several basket- or bowl-shaped analogues of the classical calix[n] arenes which have been used in supramolecular complexation studies with the fullerenes. These have included mainly cyclotriveratrylenes ( CTV ), cavitands and their derivatives, and but these will not be dealt with here. Instead this review... 

Li M-J, Huang C-H, Lai C-C, Chiu S-H (2012) Hemicarceplex formation with a cyclotriveratrylene-based molecular cage allows isolation of high-purity (>99.0%) C70 directly from fullerene extracts. Org Lett 14 6146-6149... 

This review focuses on the heterocyclic molecules such as porphyrins and the analogues (Sect. 2.1), and carbohydrates (Sect. 2.6) as host molecules for fullerenes. Therefore, references are provided here for other excellent receptors for fullerenes such as calixarenes [11-19], cyclotriveratrylene [15,20-22] and carbon nanorings [23-28]. 

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