Electrical and magnetic properties of the new conductors: (TMDTP)2 AsF6 and (TMDOP)2 AsF6

From the donor molecules tetramethyldithiapyrene (TMDTP) and the oxygen analogue tetramethyldioxapyrene (TMDOP), single crystals with composition (TMDTP)2AsF6 and (TMDOP)2AsF6 were prepared by electrocrystallization. In spite of the similar donor molecule structure and the same stoichiometry they exhibit quite different properties. (TMDTP)2AsF6 has metallic-like properties at high temperature (σRT≈1 S/cm, SRT≈20 μV/K, χPauli,RT = 3.8×10−4 emu/mol) with a metal-insulator transition at ca. 75 K, while the resistance of (TMDOP)2AsF6 shows an activated behaviour, in agreement with charge localization suggested by the thermopower results (SRT≈48 μV/K).