Crystal Structure and Conductivity of Chiral Radical Ion Salts (Me2ET)2X

Radical ion salts of both chiral (R,R) and racemic organic donor, (Me2ET)2X (Me2ET = trans-dimethylbis(ethylenedithio)tetrathiafulvalene, X = PF6, ClO4, and ReO4) were electrochemically prepared and their crystal structures were analyzed. The donor molecules are stacked in a twist-type column to reduce steric repulsion caused by methyl groups. The anions are contained in the cavities formed both by methylated and unsubstituted ethylene groups of the donor molecules, and their orientation is fixed through hydrogen bonds to methine and methylene protons. The structural difference between chiral and racemic salts is discussed. In spite of the difference in the crystal structure, their conductivity is almost identical, reflecting similarity of side-by-side S–S contacts between the donor molecules.