Fullerides superconducting salts

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. 

The room-temperature conductivities of these compounds are usually about one or two orders of magnitude smaller than those shown in Table 12.2. Included in Table 12.3 are the superconducting (but very air-sensitive) alkali metal and alkaline earth fullerides these are compounds with three-dimensional superconductivity, where the alkali metal ions are just gegenions tucked in tetrahedral and octahedral holes in the cubic fullerene crystal structure [36]. The critical temperatures of ET salts seem to be stuck at... 

The third was the more recent discovery of superconductivity in the salts of the fullerenes, Qo, with transition temperatures [34,35] ranging from 18 K for K3Q0 to 45 K for Rb Tl C. Were it not for the fact that high-temperature superconductivity had been discovered in the cuprates [36] in 1986, the discovery of superconductivity in the fullerides at these temperatures undoubtedly would have set off a frenzy of activity among workers in condensed matter similar to that which occurred after the discovery of the cuprates. 

Determination of the superconducting properties of salts prepared from Ceo and alkali and alkaline-earth metals with relatively high transition temperatures (Tc 33 K) led to the observation that the temperature Tc for the superconductivity of these fullerides was related to the size of the metallic atoms and the lattice constant [71]. Consequently, the preparation of complexes with bigger organic donor molecules was thought to increase the Tc values and a number of charge-transfer complexes with a variety of donor molecules have been prepared [70]. 

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