Fullerene supramolecular adducts

Fullerenes C60 and C70 form supramolecular adducts with a variety of molecules, such as crown ethers, ferrocene, calixarene, and hydroquinone. In the solid state, the intermolecular interactions may involve ionic interaction, hydrogen bonding, and van der Waals forces. Figure 14.2.9 shows a part of the structure of [K(18C6)]3-C6o-(C6H5CH3)3, in which Cgg is surrounded by a pair of [K+(18C6)] complexed cations. 

Chlathrates may, in a way, be regarded as supramolecular adducts in the crystalline state. C ) forms a series of these compounds which in most cases are obtained by simple cocrystallization of their constituents. Known examples are the inclusion compounds with hydrocarbons tike pentane or nonane, etc., but chlathrates of Qo or C70 have also been found with hydroquinone in the presence of benzene. In these cases the fullerene molecules occupy interstitial spaces within the crystal structure of hydroquinone and form donor-acceptor complexes. Further inclusion compounds with fuUerenes are known for ferrocene and other inorganic substances such as sulfur (Sg), white phosphorus (P4) or complexes hke (PhCN)2PdCl2 and PhsPAuCl (also refer to Section 2.5.3). For the complex of > with ferrocene the crystal structure of the first is found with the latter inserted into the given gaps. The whole stracture can only exist because ferrocene is too weak a reducing agent to transform > into Qo. 

The Bingel macrocyclization has been increasingly exploited in the construction of molecular building blocks for supramolecular systems. For this purpose, cis-2 bis-adducts, such as 43 with a m-xylylene tether (Scheme 7-8), have been particularly useful. Thus, bis-adducts 55 [70], a fullerene-glycodendron conjugate, and 56 [71] were shown to form stable Langmuir monolayers at the air-water interface (Scheme 7-9). 

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