Syntheses and characterisation of terephthalonitrile radical salts

Two terephthalonitrile radical salts have been synthesized, isolated and characterized as Li⁺(tpn)˙^-(THF)₂ and Na⁺(tpn)˙^-(THF) (tpn = terephthalonitrile; THF = tetrahydrofuran). Single crystal X-ray diffraction reveals that the lithium and sodium ions are bridged by tpn˙^- and further coordinated by THF solvent molecules, forming 1-D and 3-D coordination networks, respectively. While the lithium salt exhibits paramagnetic behaviour, the sodium analogue is diamagnetic in the solid state due to strong π-π interactions between tightly stacked tpn˙^- pairs. These readily isolable radical salts are versatile precursors for cross-coupling reactions and mild organic reductants, and could be used as attractive ligands for designing high temperature molecular magnets and conductive materials.