Synthesis and Physical Properties of Salphen‐Conjugated TTF‐Metal Complex [CuII(TTF‐Salphen)]2PF6

A paramagnetic metal complex, [Cu^II(TTF‐Salphen)], in which a TTF (tetrathiafulvalene) ligand is coordinated through a Salphen coordination site, was synthesized as a potential candidate for a new π‐d system. Electrochemical oxidation afforded its cation radical salt, [Cu^II(TTF‐Salphen)]₂PF₆, as black, block‐shaped crystals. X‐ray crystallographic analysis revealed that both the neutral and cationic complexes possess planar structures and stack in a head‐to‐tail manner to form dimers. The 2:1 stoichiometry of the TTF‐complex to the anion in [Cu^II(TTF‐Salphen)]₂PF₆ indicates a partial oxidation state of +0.5 for the TTF moiety. Electrical conductivity measurements of [Cu^II(TTF‐Salphen)]₂PF₆ revealed semiconducting behavior, reflecting its one‐dimensional columnar structure, yielded a room‐temperature conductivity of σ_RT = 1.8 S·cm⁻¹ and an activation energy of E_a = 0.14 eV. [Cu^II(TTF‐Salphen)]₂PF₆ exhibits weak antiferromagnetic interactions between the π‐spins of the TTF moieties and the d‐spins of Cu(II) centers upon cooling, followed by the formation of singlet states by the π‐spins in the TTF moieties below 20 K. Electron spin resonance (ESR) measurements on the powder sample of [Cu^II(TTF‐Salphen)]₂PF₆ support the magnetic behavior observed in the magnetic susceptibility measurements.