Electrochemistry at BEDT-TTF organic superconductor electrodes

The electron donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) forms two-dimensional-metallic, semiconducting and superconducting charge transfer salts with various pseudohalides, e.g. (BEDT-TTF)2I3 and metal pseudohalide complexes, e.g. (BEDT-TTF)2Cu(SCN)2. The highest superconducting critical temperature, Tc, currently found for these materials is 11.4 K. In addition to two phases similar to the segregated stacks of anions and cations, which is the predominate structure found in one-dimensional organic metals, a κ-phase is composed of layers of orthogonally arranged BEDT-TTF dimers separated by a planar anion layer. In all of these materials intermolecular S-S interactions provide the two-dimensional character necessary for the onset of a superconducting transition. Cyclic voltammetry is used to determine the useful range for single crystal electrodes prepared from BEDT-TTF salts of several anions. The processes occurring during the oxidation and reduction of the electrode materials are discussed. Differences in the cyclic voltammetry of different phases, i.e. stacks vs. layers of orthogonal dimers, are investigated. The cyclic voltammetric behavior of these systems are compared to the corresponding TTF salts