Novel Solid State Materials Derived from Transition Metal Bis-dithiolene Complexes

The transition metal bis-dithiolene complexes (MS4C4X4) can be used as acceptor molecules in π-donor-acceptor-type compounds, or as radical anions in mixed valence compounds. These compounds are in the wide middle ground between the strictly organic or inorganic molecular solids on which extensive research has led to the discovery of molecular superconductors and to the development of new materials and concepts. Novel solid state materials derived from metal bis-dithiolene complexes also exhibit interesting original physical properties. In the (TTF)[MS4C4(CF3)4] series of compounds, depending on the nature of the metal ion, a wide range of novel magnetic phenomena ranging from bulk ferrimagnetism (M = Ni) to spin-Peierls transition (M = Cu and Au) have been observed. Metal bis-dithiolene complexes have also been used for preparing molecular superconductors such as (TTF)[M(dmit)2]2 and (Me4N)0.5[Ni(dmit)2] (dmit2- = 1,3-dithiol-2-thione-4,5-dithiolate) in which the conduction mechanisms are quite different from those of the strictly organic molecular superconductors.