2,5-Bis(1,3-dithiol-2-ylidene)-2,5-dihydroselenophene (BDTS) and its ethylenedithio (EDT-BDTS) and bis(ethylenedithio) (BEDT-BDTS) derivatives, novel extended donors with a central selenium atom, have been synthesized by convenient methods. Of these, EDT-BDTS and BEDT-BDTS having outer chalcogen atoms afforded highly conducting molecular complexes with TCNQ (sigma=13 Scm(-1) on a compressed pellet).