STRUCTURAL AND PHYSICAL-PROPERTIES OF BEDO-TTF CHARGE-TRANSFER SALTS - KAPPA-PHASE WITH CF3SO3-

The synthesis, X-ray crystal structures, electron paramagnetic resonance (EPR) studies, conductivity measurements and electronic-band calculations for two new charge-transfer salts kappa-(BEDO-TTF)2CF3SO3 (I) and (BEDO-TTF)2CF3SO3(C4H8O)0.5, (II), are described. Most of the discussion concerns the former which is the first kappa-phase obtained with BEDO-TTF. This salt is metallic at room temperature (RT) (sigma(RT)=100 S cm-1) and undergoes a slow change towards semiconducting behaviour at low temperature. Simultaneously, the EPR linewidth of the kappa-phase decreases with T from ca. 60 G at 300 K, unlike the behaviour of classical kappa-phase superconductors. However, the calculated band structure of I is quite similar to those previously reported for classical kappa-phase salts. Comparison of magnetic and conductivity data allows the classification Of kappa-salts into two groups: (i) classical superconducting salts and (ii) the present salt and related materials. The properties of salts in the latter group are discussed in relation to the role of the anions.