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

Abstract

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.

Room-temperature proton transport and its effect on thermopower in a solid ionic semiconductor, TTFCOONH4

“…Although the absolute value of the conductivity is quite low in our present pellet sample due to including the effect of grain boundary, synthesis of a single crystal promises several orders of improvement in conductivity, as demonstrated in a related anilinium salt. 41 Moreover, the thermal conductivity is quite low in both cases, 0.21 W K À1 m À1 and 0.27 W K À1 m À1 in TTFCOONH 4 and TTFCOOND 4 , respectively. However, the more important point here is that a proton in a 2DSB conned between TTF layers is mobile at rt and largely inuences the thermopower.…”

Role of the Anilinium Ion on the Selective Polymerization of Anilinium 2-Acrylamide-2-methyl-1-propanesulfonate

“…The physicochemical properties and the structural arrangement of the anilinium cation provide it with a variety of applications. For example, anilinium salts can be found in surfactants [ 16 ], ionic liquids [ 17 ], ionic semiconductors [ 18 ], lasers [ 15 ], organogels [ 19 ], and monomers, usually for polyaniline synthesis [ 20 ]. This variety of applications owes to the different types of the anion (organic or inorganic), typically analogous to sulfate and sulfonate, which have the function of cation anilinium stabilization.…”

Isotope Effect of Thermopower in the TTFCOONH3Ph Single Crystal

“…The length of the central C=C bond in TTFCOO – is 1.348 Å (Table 1), which is longer than that of the non‐oxidized (pristine) TTF moiety (1.31 Å)11 and shorter than the bond length of completely oxidized TTF ·+ (1.38 Å),11 which suggests a partial oxidation state of the TTF moiety. The length of this C=C bond in TTFCOONH 3 Ph is reported to be 1.350 Å,4a which is almost the same as that in TTFCOOND 3 Ph, which indicates that their oxidation levels are quite similar. The deuteriated ammonium ions and carboxylates form a one‐dimensional salt‐bridge network, which induces a columnar molecular array of the TTF moiety.…”

“…The TTF moieties have short S ··· S contacts, less than the sum of the van der Waals radii, between the intra‐ and intercolumnar molecules, as indicated by yellow dotted lines. Moreover, many CH/π interactions are observed between the TTF moieties and phenyl groups, and also between phenyl groups and TTFCOONH 3 Ph 4a. The molecular array of TTFCOOND 3 Ph is also very similar to that of the proton form, although some hydrogen bonds and S ··· S contacts are slightly shorter by around 0.007 Å than those in the proton form (see Table 1).…”

“…Anilinium tetrathiafulvalene‐2‐carboxylate (TTFCOONH 3 Ph; Scheme 1) is the first semiconducting system to be grown as single crystals;4 its electrical conductivity at room temperature is quite high at 0.16 S/cm, and it has a small activation energy ( E a ) of 0.11 eV 4a. The deuterium‐substituted form (TTFCOOND 3 Ph) exhibits very similar conductivity with 0.18 S/cm and an E a of 0.12 eV 4b.…”