On the basis of three new building blocks, dithieno[3,2- b:2',3'- d]selenophene ( tt-DTS), diseleno[3,2- b:2',3'- d]thiophene ( tt-DST), and diseleno[3,2- b:2',3'- d]selenophene ( tt-DSS), four thiophene- and selenophene-based heteroacenes (3a-d) with up to seven fused rings were designed and synthesized. Another two selenophene-based heteroacenes (1 and 2) with three and five fused rings were prepared. The molecular structures of 1, 2, 3a, and 3c were confirmed by single-crystal analysis. The results showed that molecular structures, spectroscopy features, and cyclic voltammetry behaviors could be modulated by changing the heteroatoms from sulfur to selenium for 3a-d or changing the numbers of selenophene rings for 1, 2, and 3d.