T. O. Poehler

Ditetramethyltetraselenafulvalenium fluorosulfonate: The effect of a dipolar anion on the solid state physical properties of the (TMTSF)2X phase

The solid state properties of the title compound are described. The material undergoes a metal to insulator transition at 86 K which is not driven by spin density waves. The metal to insulator transition is reflected by very sharp changes in conductivity and magnetic susceptibility.

Tetramethyldithiadiselenafulvalene (TMDTDSF): Properties of its hexafluorophosphate salt and alloys with tetramethyltetraselenafulvalene

Preparation and some properties of tetramethyldithiadiselenafulvalene (TMDTDSF) are described. It forms the expected (donor)2 X salts. Properties of the PF−6 salt are described as well as properties of alloys of the title compound with tetramethyltetraselenafulvalene (TMTSF). (TMDTDSF)2PF6 is a relatively poor conductor even though it is isomorphous with the high‐pressure superconductor (TMTSF)2PF6. The profound difference in properties between these two solids is ascribed to disorder in the arrangement of sulfur and selenium atoms along the donor stacks in (TMDTDSF)2PF6. Alloying very small amounts of TMDTDSF into (TMTSF)2PF6 causes the metal‐to‐insulator transition temperature (TMI) to move up smoothly from 11 K for pure (TMTSF)2PF6 to ∼200 K for pure (TMDTDSF)2PF6 due to increasing disorder as TMDTDSF is incorporated.