Extended fullerenes

Excitonic emission, F state, 35 380-381 Exogenous ligand binding, [M-3Fe0134S] clusters, 38 365-368 Explosion calorimetry, 24 10 Extended fullerenes, 44 2... 

This review describes the preparation, characterization, and properties of all nonpolymeric complexes that contain a metal removed from the fullerene also are included. The article does not cover the essentially ionic fullerides MmC (4) or the endohedral metallofullerenes MmC (8), which have been reviewed previously. The extended fullerenes, or so-called carbon nanotubes, which have hollow centers and can be filled with metal salts, also are not discussed. The majority of complexes involve 7r-bonds and, apart from alkyl lithium fullerides, the potentially useful synthetic area of o- complexes has not been explored. Table I shows the occurrence of metal-bound adducts across the periodic table. 

Kalbac, M., Kavan, L., Zukalova, M., and Dunsch, L. (2007) The influence of an extended fullerene cage a study of chemical and electrochemical doping of C70 peapods by in situ Raman spectro-electrochemistry. J. Phys. Chem. C, 111, 1079-1085. 

I he results of their calculations were summarised in two rules. The first rule states that at least one isomer C with a properly closed p shell (i.e. bonding HOMO, antibonding I. U.MO) exists for all n = 60 - - 6k (k = 0,2,3,..., but not 1). Thus Qg, C72, Cyg, etc., are in lhi-< group. The second rule is for carbon cylinders and states that a closed-shell structure is lound for n = 2p(7 - - 3fc) (for all k). C70 is the parent of this family. The calculations Were extended to cover different types of structure and fullerenes doped with metals. 

Magnetic field effects on the reaction kinetics or yields of photochemical reactions in the condensed phase have been studied [20-23]. They have proved powerful for verifying the mechanism of photochemical reactions including triplet states. Previously, we obtained photogenerated triplet biradicals of donor-acceptor linked compounds, and found that the lifetimes of the biradicals were remarkably extended in the presence of magnetic fields up to 1T [24]. It has been reported that Cgo and its derivatives form optically transparent microscopic clusters in mixed solvents [25,26]. The clustering behavior of fullerene (C o) is mainly associated with the strong three-dimensional hydrophobic interactions between the C o units. Photoinduced... 

Given the interest in extended carbon systems in recent years, it seemed useful to study the solubility of C60 (fullerene) in various organic liquids.54 55 It was now for the solvents that the molecular surface properties were computed. The resulting Eq. (14) shows that, for this large nonpolar solute, solubility is enhanced by solvent molecule surface area and by the latter having somewhat... 

Radical polymerization of maleic anhydride and fullerene was used to obtain a new material, the photodynamic properties of which have been studied in vitro and in vivo. HeLa and bone tumor cell growth were inhibited by treatment with fullerene and light, so the polymer was tested on mice affected by bone tumor. After injection and irradiation, tumor size and weight were reduced and the mouse survival time was extended (Jiang and Li, 2007). The photodynamic properties of a supramolecular cucurbit[8]uril-fullerene complex have been studied by the same authors (Jiang and Li, 2006) who attributed HeLa cell death mainly to the damage of membrane phosphohpids and proteins. 

Previously (Cataldo and Braun, 2007), it has been noted the interesting correlation between C60 fullerene solubility and the unsaturation level of the fatty acids present in the vegetable oils and measured by the iodine number , an analytical test, which determines the number of double bonds present in the oil by the addition of iodine (Martinenghi, 1963). This correlation is confirmed for C also with the new measurements and is extendable also to C, . The correla-tion is shown in Fig. 13.1 and suggests that the solubility S expressed in milligrams per litre (mg/1) is linked to the iodine number of the oil (NI) according to the following equations ... 

Recently, we performed theoretical study of solubility of C60 in various solvents (Toropov et al., 2007a). In this study, the extended experimental data on fullerene C60 solubility in organic solvents was taken from Huanxiang et al. (2005). 

For synthetic chemists, who are interested in the transformation of known and the creation of new matter, elemental carbon as starting material once played a minor role. This situahon changed dramatically when the family of carbon allotropes consisting of the classical forms graphite and diamond became enriched by the fullerenes. In contrast to graphite and diamond, with extended solid state stmctures, fullerenes are spherical molecules and are soluble in various organic solvents, an important requirement for chemical manipulations. 

In solid-state NMR [1,51-64], the magnetic coupling between the fullerene anions has to be taken into accoimt. In the case of metal intercalated fullerides that have metallic properties a contribution from the conduction electrons must be added, a phenomenon called the Knight shift . Even if this additional shift affects the C-chemical resonance, the correspondence between extended and discrete systems of comparable Cjq oxidation state is quite close [1]. 

Reaction of 217 with Cjq leads to the amino-protected porphyrin-fulleropyrroli-dine, which can easily be deprotected to the corresponding amine [229, 277]. By further functionalization via amide coupling an easy access to extended donor-acceptor systems is possible. A carotene-porphyrin-fullerene triad was prepared by reaction of the amine with the appropriate carotene acid chloride. The motivation for the synthesis of all these donor-acceptor systems is the attempt to understand and imitate the photosynthetic process. On that score, a model for an artificial photosynthetic antenna-reaction center complex has been achieved by attaching five porphyrin cores in a dendrimer-like fashion to the fullerene [242]. 

Determination of the absolute configurations of these optically active fullerene derivatives was possible by comparison of their experimental and calculated circular dichroism (CD) spectra [96]. Tether controlled bis-cyclopropanation reactions have been extensively used to synthesize extended fimctional architectures such as dyads. 

The conjugated C-atoms of a fullerene respond to the deviation from planarity by rehybridization of the sp o and the p Jt orbitals, since pure p character of Jt orbitals is only possible in strictly planar situations ]56]. The electronic struchue of non-planar organic molecules has been analyzed by Haddon using the Jt orbital axis vector (POAV) analysis. For Cjq an average o bond hybridization of sp and a fractional s character of 0.085 (POAVl) or 0.081 (POAV2) was foimd ]59-63]. Consequently, the Jt orbitals extend further beyond the outer surface than into the interior of Cgg. This consideration implies, moreover, that fullerenes and, in particular, Cgg are fairly electronegative molecules [64, 65] since, due to the rehybridization, low-lying Jt orbitals also exhibit considerable s character. 

Extended networks of nanoparticles can be created using electrostatic interactions. In a recent study, fullerenes bearing piperazynyl groups were used to assemble Au NPs capped with citrate groups [165] (Figure 3.14). 

Figure 3.14 Extended network of Au NPs and fullerenes through electrostatic interactions.

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