J. Tarres et al., A NEW FAMILY OF MOLECULAR-METALS BASED OIL BIS(ETHYLENETHIO)TETRATHIAFULVALENE (BET-TTF) AND OCTAHEDRAL COUNTERIONS, Chemistry of materials, 7(8), 1995, pp. 1558-1567
The electrochemical synthesis and physical characterization of a serie
s of new bis(ethylenethio)tetrathiafulvalene (BET-TTF) based salts, (B
ET-TTF)PF6, and (BET-TTF)(2) X (X = PF6, AsF6, and SbF6), are reported
. In all X-ray crystal structures, only the E isomer of BET-TTF is pre
sent. The (BET-TTF)PF6 (2) salt crystallizes in the centrosymmetric gr
oup P21/a, in which donors stack uniformly along the b crystallographi
c axis in a herringbone pattern with a crystal packing similar to alph
a-phases of BEDT-TTF. The three 2:1 salts crystallize in the triclinic
P-1 space group and are isostructural, being the crystal packing moti
f very similar to the beta-phases of BEDT-TTF. In salts (BET-TTF)(2)As
F6 (4) and (BET-TTF)(2)SbF6 (5) a structural disorder due to the exter
nal sulfur positions of BET-TTF is observed. Band electronic calculati
ons on these structures indicate a quasi-2D electronic character for s
alts 4 and 5. All 2:1 salts show metallic character down to similar to
100 K, where a very broad transition toward an activated conductivity
is observed. The relationships between the crystal structures, physic
al properties, and electronic structures are discussed.