Novel 2:1 EDOB-EDT-TTF radical salts with different octahedral PF6−, AsF6−, and SbF6− anions were prepared by electrochemical oxidation. AsF6 salt was found to be isostructural to PF6 salt and had a triclinic crystal structure, while SbF6 salt was not isostructural with PF6 salt and had monoclinic crystal structure. PF6 salt had higher metal-to-semiconductor (MS) transition temperature, than that of AsF6 salt, while SbF6 salt exhibited semiconductive behavior throughout the temperature range of electrical conductivity measurements. To clarify MS transition of these salts, thermoelectric power measurements were also carried out. Thus, thermoelectric power apparatus was constructed and measurements were performed simultaneously with thermoelectric power and electrical resistivity measurements. Crystal structural features for EDOB-EDT-TTF salts at 90, 293, 330 and 350 K, as well as conductivity, thermoelectric power measurements and band structures before and after MS transition are described.
Part of the book: Thermoelectrics for Power Generation