Ethylenedithiolo-tetrathiafulvalene

Oshima K, Mori T, hiokuchi H, Urayama H, Yamochi H, Saito G (1988) Shubnikov-de Haas effect and the Eermi surface in an ambient-pressure organic superconductor (bis (ethylenedithiolo)tetrathiafulvalene)2Cu(NCS)2. Phys Rev B 38 938-941... 

Recently, Heiberg et al. [26] have studied polarizabilities of the intermolecular contacts in bis(ethylenedithiolo)tetrathiafulvalene (BEDT-TTF) and bis(ethylenedioxy)tetrathiafulvalene (BEDO-TTF) molecular crystals by polarizing microscope techniques. The principal refractive indices and the corresponding optical axes have been calculated by tensorial addition of the bond polarizabilities of all bonds in the molecules. Comparison of calculated and measured values of the relative polarizabilities showed that the polarizabilities of the molecules only cannot yield the measured indicatrix and axes angle. Thus polarizabilities with other orientations must be involved. From the crystal structure of the molecular crystals it is known that 10 and four different contacts exist between the molecules of BEDT-TTF and BEDO-TTF, respectively, with contact distances lower than van der Waals distances. Assigning of polarizabilities of these contacts can explain the measured behavior. 

The salts of this series [BEDT-TTF = bis(ethylenedithiolo)tetrathiafulvalene], with X = AuBr2, CuCl2, or Ag(CN)2, are all semiconductors with narrow band widths and strong Coulomb repulsions. For this series the magnetic susceptibility has room-temperature values of = 8 to 9 x 10 4 emu/mol, and maximum values of = 16 to 18 x 10 4 emu/mol, at TM = 60 to 70 K. However, it does not fit well a Bonner-Fisher law in any case. A spin-Peierls transition is found to occur, at 7 K, for the Ag(CN)2 salt only [65]. 

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

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