Fullerene adduct

Scheme 3. J efro-addition of 23 and 24 under MALDI-TOF MS conditions generates the ions of the mono-fullerene adducts of cydo-Ci (25" ) and cydo-C.20 (26" ), respectively [61]...

The formation of several pyrazolylpyrazolino[60]fullerene adducts (208a-c) from nitrile imines have been described (Scheme 9.64) [111]. The nitrile imines are generated in situ from the corresponding hydrazone 205 and NBS in the presence of Et3N... 

Klumpp C, Lacerda L, Chaloin O, Da Ros T, Kostarelos K, Prato M, Bianco A (2007) Multifunctionalised cationic fullerene adducts for gene transfer Design, synthesis and DNA complexation. Chem. Commun. 3762-3764. 

The two most commonly used derivatization methods for exohedral functionalization are the nucleophilic cyclopropanation with malonates (Bingel, 1993) and the formation of fulleropyrrolidines (Maggini et al., 1993). Both of these protocols have been used extensively to produce water-soluble fullerenes for biomedical applications. Other stable water-soluble fullerene adducts have also been reported (Hirsch and Brettreich, 2005). Sections 3.2.2-3.2.5 will give a short overview on the state-of-the-art of water-soluble fullerene derivatives and outline some general trends for designing such molecular structures. 

Unfortunately, these nonionic but polar fullerene adducts exhibit virtually no water solubility over the whole pH range, indicating that even four polyethylene units are not sufficient to provide tme water solubility. However, as mentioned before for other fulleienes, by diluting DMSO solutions with various amounts of water stable aqueous phases containing dispersed fullerenes can be obtained. 

Rhodium-catalyzed three-component domino coupling of 1,6-diyne 41, hydrosilane, and Cgo proceeds to give fullerene adduct 42 in good yield (Eq. 10) [29]. In this case, dienophile Cgo does not interfere with the silylcarbocyclization process and traps the 1,2-bis-exo-methylidenecyclopentane intermediates to furnish the corresponding Cgo-linked carbo- or heterocycle 42. 

It can be also very important for determining the number of isomers of higher fullerenes of regioisomers of exohedral fullerene adducts and for carrying out mechanistic investigations on the escape of the endohedral guest and reversible addition reactions [125]. The Xe NMR spectrum ofXe C5Q has also been reported [126]. 

Silylmethylation of fullerenes can be achieved by Grignard reaction of Cjq with Me2Si(0 Pr)MgCl (Scheme 3.4). Two different types of silylmethylated 1,2-fullerene adducts are formed [8]. The use of different solvents leads either to the 1,2-product 12 or to the unprecedented 1,4-addition product 13. These compounds react easily with various alcohols or phenols, which makes silylmethylated fullerenes a versatile starting material for regioselectively defined fullerene compounds [10]. Some examples are shown in Scheme 3.4. 

The bis-dienes 13-15 form ladder-type bis-fullerene adducts. Cycloadditions proceed in good yields also with electron-deficient dienes such as 21-23. Porphyrin donor systems such as 25 or 30 or quinoidal acceptor systems such as 19 and 20 were introduced to study the properties of the charge transfer in Cjq donor-acceptor systems. 

Derivatizing Cjq with a strong acceptor, such as the tetracyanoquinodimethane 231 yields organofullerenes that can accept up to eight electrons in solution [263, 278]. The acceptor ability of the quinodimethane moiety in the fullerene adduct is... 

The pronounced reactivity towards radicals is also preserved in fullerene adducts. 

In general, addihon products of Cjq tend to revert to the parent fullerene by eliminahng the addends. This aspect wiU be discussed in more detail in Sechon 14.4, since the retention of the shuctural type has been frequently used as aromaticity criterion. However, in many cases exohedral fullerene adducts exhibit thermal and chemical stability that is high enough to allow their use as building blocks in synthetic chemistry and technological applications. 

Comparable alternations between the [6,6]- and [5,6]- bond lengths are observed in many fullerene adducts and higher fullerenes. Moreover, from the evaluation of many exohedral transformation of fullerenes, in particular Cjq, an important principle of fullerene chemistry can be deduced, namely minimization of[5,6]-douhle bonds in the lowest energy Kekule structure. Minimization of [5,6]-double bonds is... 

Cyclic silylphosphanes, see Silylphosphanes, phosphorus-rich, cyclic Cyclic sulfur-nitrogen compounds, see Sulfur-nitrogen compounds, cyclic Cyclic trithiolate ligand, 38 8-9 Cyclic voltammetry A. chroococcum Fd 1, 38 130-131 fullerene adducts, 44 19 nickel(ll) macrocyclic complexes, 44 112 Rieske proteins, 47 138, 139 Cyclidenes, as cobalt complex ligands, 44 282-284... 

Electric fleld gradient, 22 214-218 Electroabsorption spectroscopy, 41 279 class II mixed-valence complexes, 41 289, 291, 294-297 [j(jl-pyz)]=+, 41 294, 296 Electrocatalytic reduction, nickel(n) macro-cyclic complexes, 44 119-121 Electrochemical interconversions, heteronuclear gold cluster compounds, 39 338-339 Electrochemical oxidation, of iron triazenide complexes, 30 21 Electrochemical properties fullerene adducts, 44 19-21, 33-34 nickeljll) macrocyclic complexes, 44 112-113... 

Elemental analysis, fullerene adducts, 44 21 Elemental technetium, see Technetium Element displacement principle, 28 167-198 applications, 28 172-176 theory, 28 169-171 Elements... 

Multimetallic fullerene adducts, 44 24, 26-28 Multinuclear metalloenzymes, 44 247-258 nt Multiple bonds, 33 260 structure of and proofs for, 33 256 Muonic radical, formation and reactions of, 28 122-130... 

F. Regioselective Self-sensitized Oxygenation of Fullerene Adducts. 857... 

TABLE 15. Regioselectivity in the self-sensitized oxygenation of fullerene adducts"... 

Zhang S, Lukoyanova O, Echegoyen L (2006) Synthesis of fullerene adducts with terpyridyl-or pyridylpyrrolidine groups in trans-1 positions. Chem Eur J 12 2846-2853... 

A wide variety of fullerene adducts have been synthesized by covalent addition... 

SCHEME 27. Transition states leading to the major and the minor allylic hydroperoxides for the self-photooxygenation reactions of [60]fullerene adducts 102-106... 

The most widely used method for the synthesis of n metal fullerene adducts involves the standard procedure of displacement by the fullerene of a ligand that is weakly bound to the metal. The ligand may be PPh3, an alkene, or even CO under favorable conditions (Scheme 2). Also, reductive elimination of H2 has been used. 

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