Superconductors, metals and magnets: Structure-property relations in molecular charge transfer salts

The broad class of molecular charge transfer salts D m X n S p where D is a conjugated electron donor molecule that forms cations in the solid state, X is an inorganic anion and S a solvent molecule, encompasses the gamut of physical properties from superconductors to low-dimensional magnets, spin-Peierls systems and metal-insulator transitions as functions of pressure and temperature. The many structure types of salts with D = BEDT-TFF {bis(ethylenedithio)-tetrahiafulvalene} and X ranging from monoatomic halide to large heteropoly-cluster ions are surveyed in the overall context of crystals as "chemically constructed multilayers", with special reference to the simultaneous presence of localized and conduction electrons.