The title compounds were designed as novel electron accepters and prepared from 4,7-dihalobenzo[1,2,5]chalcogenadiazoles in two steps. Comparisons of X-ray structures indicate that the packing arrangements of the different chalcogenadiazole derivatives are quite : different from each other in spite of their similar molecular geometries. In the crystal of the selenadiazole derivative (3) are observed very short intermolecular contacts between Se and N to form infinite "sheet"-like network, whereas coplanar dyads are formed by C-H ... N=C hydrogen bonds in the oxadiazole (1) and thiadiazole derivatives (2). These accepters afforded stable anion-radical salts upon one-electron reduction and gave highly conductive charge-transfer complexes with tetrathiafulvalene derivatives.