Synthesis and properties of novel unsymmetrical tetraselenafulvalene donors, EDT-PT-TSF and EDT-PS-TSF

In order to develop novel electron donors, by structural modification to a superior electron donor, bis(ethylenedithio)-tetraselenafulvalene (BETS 2 ), unsymmetrical TSF derivatives ethylenedithio-propylenethio-TSF (EDT-PT-TSF 5 ) and ethylenedithio-propyleneseleno-TSF (EDT-PS-TSF 6 ) have been effectively synthesized. The synthetic method involves a one-pot formation of 1,3-diselenole-2-selones from acetylene derivatives, a cross-coupling to the TSF system, and finally a ring construction of the outer heterocycles. Electrocrystallization of 5 affords a series of conductive radical cation salts with BF 4 − , PF 6 − , AsF 6 − , ClO 4 − , and SbF 6 − anions, which are of the 2:1 or 3:2 composition ratio. All of the salts with 2:1 ratio are stable metals down to 4.2 K without any specific phase transitions. X-ray crystallographic analyses confirm that they have so-called κ-type donor arrangements.