Crystal Structure and Conduction Property of the First Quasi-One-Dimensional Conductor of Tetrathiafulvalenium Salt with Mixed Inorganic Anions, (TTF) (ClO₄)_0.14±0.02(Cl)_0.424±0.08

M. Mizuno, M. Gotoh, K. Honda, I. Shibuya, and K. Aoki
[Synthetic Metals, Vol.63, No.1, pp.29-34, 1994]

The first quasi-one-dimensional tetrathiafulvalenium conductor with mixed non-stoichiometric inorganic anions, (TTF) (ClO₄)_0.14±0.02(Cl)_0.424±0.08, was crystallized electrochemically and found to have a structure of a tetragonal system with a=b=11.213(2)Å, c=3.600(1)Å, Z=2. Crystal structure was analyzed assuming the space group of P4₂/mnm. TTF radicals form stable segregated eclipsed stacks along the elongated c-axis but anions are fully disordered in the channels surrounded by the TTF stacks. The room temperature conductivity along the TTF stacks is 7-27 S/cm. The conductor shows a sharp metal-insulator transition at 253±4 K and below this temperature it behaves as a one-dimensional variable range hopping (VRH) conductor down to 70 K. Another non-stoichiometric perchlorate of TTF, (TTF) (ClO₄)_0.62±0.02, was also obtained in polycrystalline form at the same electrochemical preparation and found to have a much lower powder conductivity (7×10^-4 S/cm) which suggests a possible Peierls structure at room temperature for this compound.