Interaction between cation and anion sublattices in molecular charge transfer salts: structural conditions for ferrimagnetism

Many molecular charge transfer salts with organo-chalcogen donors and transition-metal complex anions have been synthesised in recent years in an effort to find lattices that combine conductivity with long range magnetic order, but in most cases interaction between the donor and anion sublattices is very weak. We have approached this issue by selecting anions that contain S or Se atoms capable of forming close non-bonding contacts with the donor molecules, and which also contain aromatic rings to form π–π contacts. In this way new ferrimagnets have been synthesised and characterised, with general formula D[M(NCX)4B2] where D is TTF or BEDT-TTF; M=Cr, Fe; X=S, Se; B=1,10-phenantholine, isoquinoline. We have demonstrated that cation–anion S⋯S and π⋯π contacts are necessary.