Tetramethyltetraselenafulvalene TMTSF

Exactly this approach led to the discovery of the first organic superconductors, the Bechgaard CT salts of tetramethyltetraselenafulvalene (TMTSF, 3) with various counteranions (TMTSF)2PF6 (under pressure) in 1980120 and... 

There are two groups of organic conductors which, contrary to onedimensional TCNQ salts, show considerable interchain coupling. They are both of single-stack type, with donor molecules of tetramethyltetrathia-fulvalene (TMTTF) or tetramethyltetraselenafulvalene (TMTSF) and BEDT-... 

The tetrathiafulvalene (TTF) system (12) has been in focus for a long time due to its unique properties as an excellent reversible and stable r-donor. Interest in the corresponding selena-fulvalenes culminated in 1980 <80M1 314-01,80MI 314-02) when superconductivity in an organic metal was discovered for the first time in a salt of tetramethyltetraselenafulvalene (TMTSF)jX (8). 

Molecules can assemble in varions different fashions. Among them, a relatively simple order known for aromatic molecules is a i-stacked assembly where planar aromatic molecnles form an orderly pile or heap in a co-facial manner. i-Stacked molecnles often show characteristic physical properties such as reduced photo absorption intensity (hypochromism, hypochromic effect), excimer or exciplex formation on photo excitation, and charge transport. The last property has practical importance and has been demonstrated for organic molecules and metallic complexes, such as the conducting tetrathiafulvalene (TTF)-7,7,8,8,-tetracyanoquinodimethane (TCNQ) complex where TTF and TCNQ form independent columnar stacks [13] and the tetramethyltetraselenafulvalene (TMTSF)-PFg complex where TMTSF molecules are in a stacked arrangement [14]. In either case, the stacked molecules play an important role in effectively transport a hole or an electron [15-20]. 

Since the early discovery of the large conductivity peak in TTF-TCNQ around 60 K (Coleman et al., 1973) (Fig. 6.47) many studies have been carried out on TTF-related systems (Subramanyam, 1981 Soos Klein, 1976). Some aspects related to conduction in these systems were mentioned in the previous section. (TMTSF)2C104 and related compounds (TMTSF = tetramethyltetraselenafulvalene) are found to show superconductivity at low temperatures (Jerome, 1985). 

TMTSF)2C104 [TMTSF is tetramethyltetraselenafulvalene], an ambient-pressure one-dimensional superconductor of the Bechgaard salt family... 

By using the donor TMTSF (tetramethyltetraselenafulvalene, 11b) and the newly developed technique of electrocrystallization, the groups of Bechgaard and Jerome found in 1990 the first organic superconductor, (TMTSF)2PF5, with Tj = 0.9 K at an applied pressure of 10 kbar [29]. Here the lateral two-dimensional Se-Se interactions and the applied pressure together defeat the Peierls transition. The first ambient-pressure superconductor, (TMTSF)2C104, followed quickly Fig. 4 shows its crystal structure. 

Figure 3 Examples of molecular conductor building blocks. TTF, tetrathiofulvalene TSF, tetraselena-fulvalene TMTSF, tetramethyltetraselenafulvalene TCNQ, tetracyanoquinodimethane BEDT-TTF, bis-ethylene-dithio-tetrathiofulvalene EDT-TTF, ethylene-dithio-tetrathiofulvalene dmit, dimercaptoisotri-thione or 2-thioxo-l,3-dithiole-4,5-dithiolato dmise, 2-selenoxo-l,3-dithiole-4,5-dithiolato dddt, 5,6-dihydro-...

The perrhenate anion is present in the organic superconductor materials (TMTSF)2Re04, where TMTSF = tetramethyltetraselenafulvalene, and (BEDT-TTF)4(Re04)2, where BEDT-TTF = bis(ethylenedithiolo)tetrafulvalene, and is also an important precursor to Re—Pt reforming catalysts and metathesis catalysts. The latter role has led to studies of the thermal decomposition, the laser Raman spectra and the X-ray photoelectron spectra of catalytically important perrhenates, especially NH4Re04 and Al(Re04)j. 

It is clear that the linewidth of the EPR signal is dependent on the spin-orbit coupling constants of the chalcogen atom (S or Se). For example, the S-containing salts (e.g. TMTTF, tetramethyltetrathiafulvalene) have smdler linewidths than the Se analogs (e.g. TMTSF, tetramethyltetraselenafulvalene) [2]. 

BEDT-TTF is Bis-(ethylenedithiolo)-tetrathiafulvalene, or "ET" for short ++ TMTSF is Tetramethyltetraselenafulvalene... 

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