Tetrathiafulvalene compounds superconductivity

As a final example, let us mention that Little 143,144) has discussed the possibility of obtaining organic superconductors that operate at high temperature. The first superconductive model compound to be proposed was a polymethine chain connected with highly polarizable sensitizing cyanine dyes (see e.g. Table 3). The first report on superconducting fluctuations in tetrathiafulvalene-tetra-cyanochinodimethane crystals appeared recently 145>. 2... 

TTF (tetrathiafulvalene) and related compounds have been the subject of intense interest in the materials chemistry community because of their semi-conduction and superconduction properties. Recently, TTF has emerged as a unique radical initiator because its radical cation can be easily formed. The ease of formation is presumably derived from the favorable structure of the radical cation that incorporates an aromatic disulfonium salt and a very delocalized radical [49a]. Murphy et al. demonstrated a novel one-pot reaction cascade... 

There is a long standing interest in the chemistry and the properties of cyclic compounds containing sulfur atom in modern material chemistry due to their redox chemistry. In particular, the focus has been on dithiole derivatives, e.g., dithiafulvenes and tetrathiafulvalenes, since the finding of metallic conductivity and low temperature superconductivity in radical cation salts. The quite low oxidation potentials of 1,4-dithiin compounds have been reported, recently [109]. On the other hand, thioketene dimers (2,4-bis(alkyli-dene)-l,3-dithietane) have been known for more than 100 years and synthesized by various methods [110-115]. The structure of these dimer compounds is similar to that of the redox-active sulfur compounds therefore, the potential electronic property of the thioketene dimer moiety is considerably attractive with the aim of application to a new and better -donor. 

In parallel studies, an even more interesting physical property, the superconductivity of organic materials, has been discovered. For example, 1 1 charge-transfer complexes of tetrathiafulvalene 81 (Scheme 1.24) and tetracya-noquinodimethane 82 were shown to display not only metal-like conductivity at ambient temperature but also properties of superconductors at low temperatures. Numerous compounds of this and other types were synthesized and tested. Especially promising results were obtained with charge-transfer salts of bis(ethylenedithio)tetrathiafulvalene 83 with simple inorganic anions. Some of... 

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