Syntheses and Properties of Tetrathiotetrathiafulvalene Derivatives of Cyclophane-Type Structures

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TTF derivatives having cyclophane structure have been proposed to realize new unique arrangements and intermolecular interactions of TTF units. Among them cross-cyclophane twin donors, in which long axs of TTF units are fixed in a cross orientation by four ethylendithio (1), trimethylenedithio (2), and trimethylenediseleno (3) chains, were successfully prepared. Intramolecular double couplings of macrocyclic dmit tetramers to give the central double bond of TTF units are most effective to obtain 1 and 2, whereas 3 was prepared starting from TTF.Although the donor ability of 1 was low due to a heavy bending of the donor units, that of 2 was the same as BEDT-TTF.The crystal structures of a charge transfer complex, 2・TCNQ,and an ion radical salt 2・Br (1,1,2-TCE) _2, revealed that 2 has an ability to construct characteristic self-assembled structures, recognizing a size and a shape of acceptors or counter ions.The almost isotropic conducting properties of the ion radical salt was interpreted based on the unique molecular structure of 2.The temperature dependence of the magnetic susceptibility of the salt revealed a basically paramagnetic nature of magnetic behavior, but it showed ferromagnetic interaction at lower temperatures.In spite of various attempts, twin donors, where long axs of TTF units are held parallel by four ethylendithio or trimethylendithio groups, are yet to be prepared. Conformation and /or orientation of the two TTF units arranged in a parallel fashion compared to cross or extended ones could be the reason.