Tris-fused tetrathiafulvalenes (TTF): highly conducting single-component organics and metallic charge-transfer salt

Tris-fused tetrathiafulvalene (TTF) derivatives, TTC_n-TTPY, 2,2′-bis4,5-alkylthio-(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalenylidene] with four alkylthio chains C_nH_2n+1S: n=3–5] are prepared and the structural and conducting properties are investigated. Crystals of the neutral molecules show very low electrical resistivity (400 Ω cm) as single-component pure organic materials. Irrespective of the alkylthio chain length, the crystal structures are so-called β″-type consisting of uniform stacks of the tris-fused TTF parts. Iodine-doped TTC₃-TTPY exhibits metallic conductivity down to liquid helium temperature.