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. Electro-crystallization of 5 affords a series of conductive radical cation salts with BF4-, PF6-, AsF6-, ClO4-, and SbF6- 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 kappa-type donor arrangements.