Syntheses, structures and properties of asymmetric thiophene-containing pentacene-like heteroacenes organic semiconductors

Two thiophene-containing pentacene-like semiconductors, benzo[d]naphtho[2,1-b]thiophene (BNT) and benzo[d]phenanthro[9,10-b]thiophene (BPT), were synthesized in a new route, and they were characterized by means of ultraviolet-visible absorption spectrum, thermo- and electro-chemistry analysis. Single crystals were obtained by vapor diffusion of solvent to analyze the correlation between charge transport and structure properties. The large band gaps and low-lying HOMO energy levels could result in much better stability. It was observed that the molecular packing in the herringbone motif is similar to that in pentacene, which is the benchmark of organic semiconductors. The BNT and BPT molecules form columnar π-stacking along the crystallographic a-axis direction with an interplanar separation of 3.535 and 3.442 Å, respectively, which suggests that the molecules adopt compact packing in solid state. The distances indicate the presence of π−π interactions along the intermolecular stacking axis in the two materials. Face-to-face columnar π-stacking increases the effective dimensionality of the electronic structure and benefits charge transport. Multicolor emission property was observed for both BNT and BPT thin films.