Ionic semiconductor: DC and AC conductivity of anilinium tetrathiafulvalene-2-carboxylate

A single crystal of anilinium tetrathiafulvalene-2-carboxylate exhibits a characteristic electrical conduction; it is a semiconductor with activation-type transport above 200 K; σ_rt = 0.16 S cm^-1 with an activation energy of 0.11 eV. On the other hand, below 200 K, it does not obey the Arrhenius relation but is conductive even at 4 K with 2.1 × 10 ^-4 S cm^-1 at a frequency of 2 MHz. Its behavior exhibits strong frequency dependence and suggests a particular conduction coupled with dielectric relaxation, reflecting its ionic nature. The crystal structure of the salt shows that conducting molecules are assembled supramolecularly with multiple nonbonding interactions, such as the hydrogen bond, and the π/π and CH/π interactions. The hydrogen bond and CH/π interactions have a short bond length, which is similar to the charge-assisted-type interaction observed in organometallics.