π-d interaction-based molecular conducting magnets

The crystal structures and electronic and magnetic properties of conducting molecular magnets developed by our group are reviewed, from the viewpoints of our two strategies for increasing the interaction between the conducting π-layer and magnetic d-layer (π-d interaction). (DMET)₂FeBr₄ and (EDTDM)₂ FeBr₄ is composed of quasi-one-dimensional donor sheets sandwiched between magnetic anion sheets. The ground state of the donor layer changes from the insulator state to the metallic state by the application of pressure especially for the EDTDM salt, and near the insulator-metal phase boundary pressure the magnetic order of the anion spins considerably affects the transport properties of the donor layer. The crystal structure of (EDT-TTFBr₂)₂ FeBr₄ and (EDO-TTFBr₂)₂FeX₄ (X = Cl, Br) is characterized by strong intermolecular halogen-halogen contacts between the organic donor and FeX₄^- anion molecules. The magnetic order of the anion spins and relatively high magnetic order transition temperature proves the effectiveness of the halogen-halogen contacts to strengthen the π-d interaction.