STRUCTURAL-PROPERTIES OF 2 MODIFICATIONS OF HYDRATED BEDT-TTF CHLORIDE SALTS

In this paper are presented two modifications of hydrated chlorides of bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF)x Cl2, yH2O with stoichiometries x = 3, y = 2 (I) and x = 4, y = 6 (III). The room temperature crystal structures of (I) the 3/2 stoichiometry and (II) the 4/4 stoichiometry compounds were already known. (I) has been measured at low temperature (50K) to look for the structural changes associated with the variations of the physical properties near 110K. The latter has been correlated with the modification of the thermal expansion anisotropy in the stacking direction of BEDT-TTF cations, the [010] crystallographic direction. The new 4/6 salt (III) is the third hydrated BEDT-TTF chloride known up to date. It differs from the others by the space group. As for the precedent forms one can see a 2D arrangement of anionic and ationic sheets alternating along the [100] crystallographic direction, but there are two orientations for the BEDT-TTF planes and two kinds of overlapping modes of these molecules.