BEDT-TTF salts with fluorinated sulfonate anions

A number of layered conducting BEDT-TTF, bis(ethylenedithio)tetrathiafulvalene, salts with heavily fluorinated organosulfonate anions have been prepared and characterized. Of particular interest are the salts containing SF5RSO3− anions, where R is a partially fluorinated aliphatic backbone. While structurally similar —the β″ packing type predominates—the ground state of these salts varies from superconducting in the case of β″-(BEDT-TTF)2SF5CH2CF2SO3 [1] to insulating. Many of the salts with insulating ground states are metallic at room temperature, but charge localization and disproportionation over crystallographically non-equivalent sites occurs at low temperature. The organosulfonate group exhibits a propensity to bind to lithium ions, thus ternary salts incorporating Li+ into the complex anion layer are often found. The fluorophilic effect in organofluorine compounds may be exploited to form salts where the conducting BEDT-TTF layers are separated by extremely bulky anion bilayers. The crystal structure of one such system, (BEDT-TTF)3[(CF3)2CFC2H4SO3]4(H5O2)2, is described here.