Syntheses of new TTF-based metal complexes for conducting and magnetic systems: Schiff base-type metal complex with partially oxidized TTF moiety

New TTF-based ligands (TTF=tetrathiafulvalene) with Schiff base-type coordination sites have been synthesized: 4,5-bis(4-salicylideneiminophenyl)-4',5'-ethylenedithio-TTF (1a), 4,5-bis(4-picolinideneiminophenyl)-4',5'-ethylenedithio-TTF (1b), and 4-(2-salicylideneiminoethylthio)-5-methyl-4',5'-ethylenedithio-TTF (Hsae-TTF). X-ray crystallography for 1a revealed that 1a has rigid structure around the coordination sites, which prevents it to form metal complexes. On the other hand, Hsae-TTF ligand has flexibility around its coordination sites due to alkyl chain spacer, and gave mononuclear complexes with Ni(II) and Cu(II) ions, [MII(saeTTF)2] (MII=Ni(II) and Cu(II)). The metal ions in [MII(saeTTF)2] have a square planar coordination structure with two TTF-based ligands, which was sandwiched by two neutral TTF moieties. The Cu(II) complex, [CuII(saeTTF)2], yielded charge transfer (CT) complexes with acceptors such as F4TCNQ, DDQ, and iodine. CT complexes with F4TCNQ and iodine were semiconductive, but that with DDQ was insulator. This is due to the difference of the degree of charge transfer; TTF moiety in F4TCNQ salt was partially oxidized but that of DDQ salt was completely oxidized. The radical cation salts of [CuII(saeTTF)2] with PF6- anion was also obtained in 1:1 donor and anion ratio by electrocrystallization. The donor and anion ratio indicates that the oxidation state of TTF moieties in the radical salt, [CuII(saeTTF)2]PF6, was partial oxidation state.