We synthesized vinylogous 4,5-ethylenedioxy-tetrathiafulvalenes (EDO-TTFs), 4,5-ethylenedioxy-2,2 0ethanediylidenebis(1,3-dithiole) (EDO-EBDT), 4,5-dimethyl-4 0 ,5 0 -ethylenedioxy-2,2 0 -ethanediylidenebis(1,3-dithiole) (DMEDO-EBDT), 4,5-bis(thiomethyl)-4 0 ,5 0 -ethylenedioxy-2,2 0 -ethanediylidenebis (1,3-dithiole) (BTMEDO-EBDT), and 4,5-bis(methoxycarbonyl)-4 0 ,5 0 -ethylenedioxy-2,2 0 -ethanediylidenebis(1,3-dithiole) (BMCEDO-EBDT). The cyclic voltammograms of the vinylogous EDO-TTFs show two pairs of single-electron redox waves. The first oxidation potentials (E 1 ) of vinylogous EDO-TTFs are lower than those of the related TTFs, indicating that the electron donating abilities of new donors are stronger than those of the corresponding TTFs. The smaller E 2 ร E 1 values of new donors compared with those of the related TTFs suggest a decrease in the on-site Coulombic repulsion in the dication state. X-ray crystal structure analysis of BMCEDO-EBDT reveals that the inter-molecular C-H?O type hydrogen bond is constructed between the hydrogen atom and the oxygen atom of the ethylenedioxy group. Single crystalline TCNQ complexes of DMEDO-EBDT and BTMEDO-EBDT have been prepared and their conducting properties and crystal structure have been investigated. The TCNQ complexes of DMEDO-EBDT and BTMEDO-EBDT show low electrical conductivities (s rt o 10 ร 6 S cm ร 1 for (DMEDO-EBDT)(TCNQ)(chlorobenzene) and s rt = 2.2 ร 10 ร 3 S cm ร 1 for (BTMEDO-EBDT)(TCNQ)) due to DDAAtype alternate stacking.