Metal reduction fullerenes

The lithium metal reduction of 7r-conjugated hydrocarbons and fullerenes... 

It is noted that in spite of the formally negative charge of the Cg2 cage (namely, 3-) induced by the incarcerated M + ion, the oxidation processes of the EMFs are more difficult and the reduction processes are easier with respect to the corresponding processes of free Cg2. Excluding obviously Coulombic effects, this means that the intramolecular metal ion/fullerene electron exchange modifies appreciably the nature of both the HOMO and LUMO levels with respect to those of free Cg2. as on the other hand theoretically proved [21c, 24]. 

The different reactivities depending on the solvents can be attributed to the solvation of the reaction intermediate In toluene, adduct formation is considered to proceed in the triplet exciplex on the other hand, in benzonitrile, the solvated radical ion pair can react with solvent molecules. In the case of the reaction with the La Cg2> Akasaka et al. observed adduct formation in both the photo- and thermal-reaction conditions [63]. Higher reactivity of La C82 can be attributed to the high electron acceptor ability of La C82. It has been reported in the electrochemical studies on metal encapsulated fullerenes that the reduction potential of La Cg2 shifts to the anodic direction by 0.7 V in comparison with Qo-... 

Metal-free initiators, 14 258-259 Metal fullerenes, 2 718-719 Metal-halogen exchange, in pyridine chemistry, 22 107-108 Metal hydrazides, 23 567 Metal hydrides, 23 611-613 amines by reduction, 2 493 hydrogen storage and, 23 851 nitriding, 27 206-207 storage of, 23 786... 

The three fullerene-centred reductions display features of chemical reversibility and are localized at potential values more negative by about 0.2 V than those of free C6o, Table 4. This proves that also in this case the metal fragment pushes electron density towards the fullerene. 

The first chemical transformations carried out with Cjq were reductions. After the pronounced electrophilicity of the fullerenes was recognized, electron transfer reactions with electropositive metals, organometallic compounds, strong organic donor molecules as well as electrochemical and photochemical reductions have been used to prepare fulleride salts respectively fulleride anions. Functionalized fulleride anions and salts have been mostly prepared by reactions with carbanions or by removing the proton from hydrofullerenes. Some of these systems, either functionalized or derived from pristine Cjq, exhibit extraordinary solid-state properties such as superconductivity and molecular ferromagnetism. Fullerides are promising candidates for nonlinear optical materials and may be used for enhanced photoluminescence material. 

Ultrasound-aided reduction of Cjq and C7Q with Li metal to anionic species can be carried out in THF as the solvent [50]. In contrast to the parent fullerenes, the anions Cgo"" and are very soluble in THF. Solutions generated this way are deep red-brown. Alkylation of a C50 and C q polyanion mixture with excess Mel leads to polymethylated fullerenes with up to 24 methyl groups covalently bound (see also Chapter 1). 

The electrochemical properties of TNT-EMFs, M3N C2n n > 39) differ from those of the empty cage fullerenes (see Fig. 6) due to the interaction of the metal cluster with the carbon cage and because the structure of these carbon cages are generally different. As a consequence, the reductive processes are electrochemically irreversible but chemically reversible. The oxidative processes occur at lower potentials because the HOMO orbital is mainly localized on the trimetallic nitride clusters and the HOMO-LUMO gaps in solution are smaller [25,58]. The endohedral metallo-fullerenes M C2n show similar behavior but even smaller HOMO-LUMO gaps [59]. 

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