Electrochemistry of fullerenes

Echegoyen, L. E. Echegoyen, The EleclrochemisUy ofCio and Related Compounds, in H. Lund, O. Hammerich, Organic Electrochemistry, 4th ed., Marcel Dekker, 

The choice of solvents has considerable impact on the reduction and oxidation potentials measured. The values vary up to 400 mV depending on the solution medium. Obviously factors like donor/acceptor properties, Lewis basicity, or the ability to form hydrogen bonds have large influence on the redox potential. 

The higher fullerenes are more easily reduced and oxidized than Cgo. The first reduction potential of Cys, for example, is about 100-200 mV (depending on the solvent) more positive than for Cso- Altogether the first one-electron reduction is facilitated with an increasing number of carbon atoms and the reduction potential shifts toward more positive values. Furthermore, with the LUMO degeneration removed, a wider variation is observed for the potentials of different reduction steps. Finally, the HOMO-LUMO-gap, which can be estimated from the difference between the first oxidative and the first reductive step, decreases with a growing number of carbon atoms. 

The fulleride anions generated by electrochemical reduction may be reacted with electrophiles, yielding functionalized fullerenes like, for instance, alkylated derivatives. 

The oxidation of C o should be harder to achieve due to the high ionization potential and the completely occupied HOMO. The first oxidation step of Qo has experimentally been found at a relatively high potential of +1.26V. Nevertheless, it has by now been possible to isolate a number of compounds with an oxidized Qo as well as a fairly stable salt of Qo, and the oxidation potentials to Qj (+1.71 V) andQo (+2.14 V) could be determined, too. Likewise the electrochemical oxidation of Qo succeeded the anodic potential was measured to be +1.2 V. The resulting radical cations are highly reactive and could be trapped with a variety of nucleophiles. The numerous derivatives of fullerenes naturally possess a varied electrochemistry of their own, yet a detailed discussion will be left out here to refer instead to the review hterature on the topic. 

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Echegoyen L and Echegoyen L E 1998 Electrochemistry of fullerenes and their derivatives Accou/rfs Chem. Res. 31 593-601 HIrsch A 1994 The Chemistry of the Fuiierenes (Stuttgart Thieme)... 

Electrochemistry of fullerene derivatives with heterocyclic fragments 98ACR593. 

Echegoyen L, Echegoyen LE (1998) Electrochemistry of Fullerenes and Their Derivatives. Acc. Chem. Res. 31 593-601. 

Before embarking on a detailed discussion on the electrochemistry of fullerenes, it is important to emphasize that the... 

Recently, non-oxide HTSCs such as derivatives of fullerenes [549,550] were discovered, as well as certain high-melting compounds of transition metals [551, 552]. The electrochemistry of fullerenes has already been transformed into an actively developed independent field [550,553,554]. The electrosynthesis of a number of carbides, sulfides, borides, and their analogs represents a well-known method for their production [23,555]. Hence, electrochemistry also plays an active role in the new directions of the HTSC chemistry. 

Porous carbons and nanotubes have attracted considerable attention in relation to such practical issues as hydrogen storage, lithium batteries, and supercapacitors. In general, the electrochemical behavior of porous carbons and CNTs solely consists of double-layer charging processes with small or zero contribution of faradaic pseudocapacitance of surface oxide functionalities. This is in sharp contrast with the rich electrochemistry of fullerenes. 

Goldenberg L M 1994 Electrochemical properties of Langmuir-Blodgett films J, Electroanal. Chem. 379 3-19 Chlistunoff J, Cliffel D and Bard A J 1995 Electrochemistry of fullerene films Thin Solid Films 257 166-84... 

Recently, the electrochemistry of fullerenes and their derivatives has gained much attention [33]. Cgo, C70 and higher fullerenes were reduced electrochemi-cally, and six reduction waves were observed for both Cgo and C70 [34], as well as for most of the higher fullerenes [35]. The energy levels that were obtained from these experiments were mostly in line with MO calculations. The electrochemistry of numerous fullerene derivatives was studied to compare their electron affinities and energy levels with their parent fullerenes. Electrochemically induced isomer-izations can be observed in CV, as is the case in the rearrangement of fulleroids to methanofullerenes [36]. 

Solution Electrochemistry of Fullerenes. 334 3 Electrochemistry of Fullerene Films 383... 

Since the first report on the electrochemical properties of C o in 1990 [1], there has been a growing interest in the electrochemistry of fullerenes and related molecules. This interest has been stimulated by both theoretical considerations and new experimental findings. The prediction of triple degeneracy of the LUMO... 

The present article attempts to cover the most important general aspects of the electrochemistry of fullerenes and fullerene derivatives. The chapter is divided into the following main sections solution electrochemistry of fullerenes, solution electrochemistry of fullerene derivatives, and the electrochemistry of fullerene films. Such partitioning of the article seemed most obvious in view of differences in the chemistry, methodology and theory of processes belonging to each category. 

The oxidative electrochemistry of fullerenes is not as rich as the reductive. Most of the solvent/background electrolyte combinations studied to date have too limited a potential window for the oxidation of fullerenes to be observed. Oxidation of C o was first studied by Jehoulet et al. [58] who found that a solid C o film oxidizes totally irreversibly in acetonitrile. Dubois et al. [30] found a single totally irreversible oxidation at -f-1.30 V vs. ferrocene for both 50 tmd... 

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