Tetrathiafulvalenes conducting materials

The research and development of molecular conductive materials have a long history. Akamatu [1] found that aromatic hydrocarbons are made conducting by doping with an acceptor such as iodine. After this discovery various molecular acceptors and donors were designed and synthesized. Typical examples include tetracyano-quinodimethane (TCNQ) [2,3] and tetrathiafulvalene (TTF) [3,4] and their analogs. The development of these low molecular-weight materials finally led to molecular superconductors [5] that have been supplying many researchers with active research fields. 

Solid State Properties. Perhaps as a result of the limited intermolecular interactions of these complexes in the solid state, they exhibit few solid-state properties of interest. The dianionic 7a did successfully produce a charge transfer material by mixing it with a solution of the tetrathiafulvalene-based salt (TTF)3(BF4)2. Elemental analysis of the resulting black product gave the formula (TTF)4[7a]3 and the material exhibited a conductivity of 9 x 10 S... 

Since the discovery in 1973 of metal-like conductivity in the charge transfer salt tetrathiafulvalene-tetracyano-p-quinodimethane (TTF-TCNQ, 1,-2), a host of new materials have been prepared displaying this interesting property. Widespread research on these materials has led to an improved understanding of the physics underlying the organic metallic state, and to a succession of molecular modifications which have enhanced these properties. ... 

The earliest considerations of how electrical conductivity might be associated with molecular materials emphasized the polarizability of the constituent molecules as the most important factor (65JCP(42)4307). The efforts of synthetic chemists to devise an organic conductor based solely on these ideas were unsuccessful. Discovery of the electrical conductivity in the material prepared from A-2,2 -bi-l,3-dithiolylidene (tetrathiafulvalene, TTF ... 

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. 

Conducting organic salt electrodes directly coupled to oxidases have been described such as, for example, A -methylphenazinium (NMP+) cation and tetracyanoquinodimethane (TCNQ-) anion as an electrode material for facilitating electron transfer of glucose oxidase47. Results with other salt cations, such as tetrathiafulvalene (TTF+) and quinoline (Q+), have been reported48. 

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... 

Arylstannanes reacted with 2-iodoimidazole under Stille conditions gave rise to cross-coupled products. The imidazole modified tetrathiafulvalene 362, synthesized via Stille coupling, formed a charge transfer complex with chloranil, which displayed metal like conductivity for the first time in a purely organic material (Scheme 85) <2004AGE6343>. 

Due to their structural and electrochemical properties, it would appear almost obvious to combine ferrocene-containing fragments and derivatives of tetra-thiafulvalene to construct new donors for conducting CT complexes. This approach would lead to new multistage redox systems that are likely to display different solid state properties to those of their congeners. However, only very few derivatives of this type have been so far reported. What appears to be the first compound belonging to this class was prepared by Ueno et al. in 1980 [64]. Bis(ferrocenyl)tetrathiafulvalene was obtained as a transjcis isomeric mixture (6 and 7, respectively) and was shown to form 1 1 CT complexes with TCNQ and DDQ. These materials possess... 

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