Synthesis and properties of novel heterocycle-fused TTF-type electron donors: bis(propylenethio)tetrathiafulvalene (BPT-TTF), bis(propyleneseleno)tetrathiafulvalene (BPS-TTF), and their tetraselenafulvalene analogues (BPT-TSF and BPS-TSF)

A series of novel heterocycle-fused TTF-type electron donors, bis(propylene thio)tetrathiafulvalene (BPT-TTF, 5), bis(propyleneseleno)tetrathiafulvalen e (BPS-TTF, 6), and their tetraselenafulvalene analogues (BPT-TSF, 7 and BP S-TSF, 8) have been effectively synthesized from a common starting compound , THP-protected pent-4-yn-1-ol. The solution electrochemistry reveals that all the new donors have good electron donating properties. Formation of the ir radical cation salts by electrocrystallization technique has been succes sfully achieved. All the radical salts derived from the TTF derivatives (5 and 6) are insulating owing to the complete charge transfer. On the other h and, the TSF derivatives (7 and 8) afford different types of highly conduct ive radical cation salts. Of these, 7 . PF6, 7 . AsF6 and 7 . FeCl4 remain metallic down to liquid helium temperature.