New organic superconductors in the system (ET)(2)M(CF3)(4)(solvent) (M=Cu,Ag,Au): Dramatic effects of organometallic anion and solvent replacement

Over twenty molecular-based superconductors have been synthesized recently via electrocrystallization of the organic bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) electron donor molecule with the novel organometallic M(CF3)(4)(-) (M = Cu, Ag, and Au) anions in a variety of 1,1,2-trihaloethane solvents. The highly anisotropic physical properties of these solvated (ET)(2)M(CF3)(4)(1,1,2-trihaloethane) salts can be tuned via modifications of each of their three discrete molecular components. These unique salts crystallize in two distinct structural modifications of the kappa-type packing motif (sheets of dimerized electron-donor molecules arranged in a parquet fashion). Crystals of the lower T-c phase (kappa(L)) have a plate-like morphology and superconducting transition temperatures in the 2 - 6 K range, while the transitions of the higher T-c phase (kappa(H)), which typically have a needle-like morphology, are in the 9 - 11 K range. The synthesis.