Radicals fullerene

Accordingly, the exterior surface is much more reactive than planar analogues, and is comparable to those of electron deficient polyolefins. This, in turn, rationalizes the high reactivity of the fullerene core towards photolytically and radiolytically generated carbon- and heteroatomic-centred radicals and also other neutral or ionic species [8]. The interior, in contrast, is shown to be practically inert [9]. Despite these surface related effects, the... 

One aspect that reflects the electronic configuration of fullerenes relates to the electrochemically induced reduction and oxidation processes in solution. In good agreement with the tlireefold degenerate LUMO, the redox chemistry of [60]fullerene, investigated primarily with cyclic voltammetry and Osteryoung square wave voltammetry, unravels six reversible, one-electron reduction steps with potentials that are equally separated from each other. The separation between any two successive reduction steps is -450 50 mV. The low reduction potential (only -0.44 V versus SCE) of the process, that corresponds to the generation of the rt-radical anion 131,109,110,111 and 1121, deserves special attention. 

There are, indeed, many biological implications that have been triggered by the advent of fullerenes. They range from potential inhibition of HIV-1 protease, synthesis of dmgs for photodynamic therapy and free radical scavenging (antioxidants), to participation in photo-induced DNA scission processes [156, 157, 158, 159, 160, 161, 162 and 163]. These examples unequivocally demonstrate the particular importance of water-soluble fullerenes and are summarized in a few excellent reviews [141, 1751. 

Azamar-Barrios J A, Munoz E P and Penicaud A 1997 Electrochemical generation of the higher fullerene radicals Tmoisture-free conditions and their observation by EPR J. Chem. Soc.,... 

Carbonera D, DiValentin M, Corva]a C, Agostini G, Giacometti G, Liddell P A, Kuciauskas D, Moore A L, Moore T A and Gust D 1998 EPR investigation of photoinduced radical pair formation and decay to a triplet state in a carotene-porphyrin-fullerene triad J. Am. Chem. Soc. 120 4398-405... 

Phosphonyl radicals have been used to functionalize the (60)-, (70)- and (76)-fullerenes [35]. Radical phosphonylation (Scheme 12) of alkenes has been developed by Motherwell et al. [36] for the preparation of fluorophosphony-lated analogs of riboses that exhibit high potential biological activity [37]. 

This paper is concerned with the structures of the simplest possible adducts of the Ceo and C70 fullerenes, namely the monohydrides, CmH and C H. These open shell species or radicals may be considered as the product of the addition of one atom of hydrogen or one of its isotopes, among which we include specifically the light pseudoisotope of hydrogen known as muonium. Mu = pfe. Although Ceo//has been observed [1], the stimulus for these calculations arose from the experiments on muon implantation in solid [2,3] and C70 [4]. 

Foote, C.S. Photophysical and Photochemical Properties of Fullerenes. 169,347-364 (1994). Fossey, J., Sorba, J., and Lefort, D. Peracide and Free Radicals A Theoretical and Experimental Approach. 164, 99-113 (1993). 

Balance equations, for a mixture, 24 669-671 Balances 26 227 analytical, 26 245 precision, 26 245 Balke process, 17 139 B-Alkyl-9-BBN derivatives, 13 658 B-Alkylcatecholboranes, free-radical oxidations of, 13 648 Ball and chain structures, fullerene, 12 252... 

Enes et al. (2006) recently presented new fulleropyrrolidines bearing one or two 3,5-di-tert-bvAy 1-4-hydroxyphcny 1 units, the EPR studies of which demonstrated that these derivatives are antioxidants. In this case, the presence of the fullerene unit seems to play a marginal role in the reaction with peroxyl radicals, which is governed by the phenol portion. Despite this, the presence of C60 should contribute to scavenge radicals in hypoxic conditions, where alkyl radicals could be the main oxidative products to be removed. 

Novel nitroxide malonate methanofullerenes (Fig. 1.3), thanks to the presence of nitroxide radicals and fullerene moiety, are able to protect cells from toxic side effects of cyclophosphamide (Gubskaya et al., 2007). Experiments were carried out on mice, in which leukemia P-388 was transplanted. Cyclophosphamide or fullerene individually injected did not increase the average life span of the animals, while the combination of the anticancer drug and nitroxide fullerene derivative resulted in the survival of 70% animals, classifying these compounds as promising modifiers of biological reaction for tumor therapy. 

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. 

In other cases fullerene antibacterial action takes place after photoirradiation of fulleropyrrolidinium salts. It is not yet clear if the photodynamic action implies the participation of superoxide and hydroxyl radicals (type I mechanism) or singlet oxygen (type II mechanism) but the efficacy is really interesting with the death of more than 99.9% of bacterial and fungal cells and a special selectivity for microbes over mammalian cells (Tegos et al., 2005). Also a sulfobutyl fullerene derivative is able to inhibit environmental bacteria after photoirradiation and it exerts its action on E. coli even if incorporated in coated polymer (Yu et al., 2005). 

Xiao L, Takada H, Gan XH, Miwa N (2006) The water-soluble fullerene derivative Radical Sponge exerts cytoprotective action against UVA irradiation but not visible-light-catalyzed cytotoxicity in human skin keratinocytes. Bioorg. Med. Chem. Lett. 16 1590-1595. 

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