Structural aspects of the phase transitions in (BEDO-TTF)2ReO4·H2O

The effect of the first-order phase transition occurring around 220K on the crystal and electronic structure of the molecular superconductor (BEDO-TTF)2ReO4·H2O has been studied. The crystal structure at 170K has been determined and it is found that the main structural change resulting from the phase transition is connected with a rotation of the ReO4− anions. This rotation leads to changes in the S…S and S…O intermolecular contacts within the BEDO-TTF donor layers, nevertheless the band structure is remained practically unchanged. Possible changes in the crystal structure which can occur at room temperature depending on the experimental conditions are considered. It seems very likely that the (BEDO-TTF)2ReO4·H2O crystal loses its water molecules in the vacuum and hence changes its crystal structure.