Multistability in a family of DT-TTF organic radical based compounds (DT-TTF)(4)[M(L)(2)](3) (M = Au, Cu; L = pds, pdt, bdt)

The preparation of new charge transfer salts based on the DT-TTF donor and monoanionic square planar transition metal bisdichalcogenide complexes M(L)(2) (M = Au, Cu; L = pds, pdt, bdt, where pds = pyrazine-1,2-diselenolate, pdt = pyrazine- 1,2-dithiolate, bdt = benzene-1,2-dithiolate) are reported and these salts are characterized by X-ray diffraction, EPR spectroscopy, electrical conductivity, thermoelectric power and static magnetization measurements, as well as tight-binding band structure calculations. Three compounds, (DT-TTF)(4)[Au-III(bdt)(2)](3), (DT-TTF)(4)[Cu-III(pds)(2)](3), (DT-TTF)(4)[Cu-III(pdt)(2)](3), are members of a general family of compounds of DT-TTF with stoichiometry 4 : 3 as the previously reported (DT-TTF)(4)[AuIII(pds)(2)](3). Although not strictly isostructural, all members of this family present a similar crystal packing motif of the donor and acceptor units and present a common pattern of first- and second-order phase transitions as seen in electrical transport and magnetic properties. The second-order phase transition is ascribed to a variation from dynamic to static charge ordering. With [Cu-III(pdt)(2)] and DT-TTF a 1 : 1 salt with formula (DT-TTF)[Cu-III(pdt)(2)] was also obtained. The structural differences and similarities between the four compounds (DT-TTF)(4)[M(L)(2)](3) (M = Au, Cu; L = pds, pdt, bdt), that are related to their physical properties, and the reversible phase transitions observed are discussed.