Metallic and superconducting salts based on an unsymmetrical π-donor dimethyl(ethylenedithio)tetraselenafulvalene (DMET-TSeF)

A series of radical cation salts (DMET-TSeF)2X (X=I3, AuI2, AuBr2, AuCl2, Au(CN)2) crystallize in the triclinic P anti 1 group. The DMET-TSeF molecules form zigzag columnar stacks. Short intermolecular chalcogen..chalcogen contacts are observed within and between stacks. The AuI2 salt exhibits a sample-dependent resistivity minimum around 25 K. The AuI2 salt without the resistivity minimum shows superconductivity with Tc = 0.58 K at ambient pressure. The AuBr2 salt exhibits a resistivity minimum around 35 K. Other salts remain metallic down to 4.2 K. These salts should be classified into a quasi one-dimensional system. (orig.)