RESUMO
2,5-Di(trimethylsilanyl)dithieno[2,3-b:3',2'-d]thiophene ((TMS)2-bb-DTT), 2,5-di(trimethylsilanyl)diseleno[2,3-b:3',2'-d]thiophene ((TMS)2-bb-DST), and 2,5-di(trimethylsilanyl)diseleno[2,3-b:3',2'-d] selenophene ((TMS)2-bb-DSS) were used as starting materials to synthesize three S-shaped double helicenes (i.e., DH-1, DH-2, and DH-3) through monobromination, formylation, the Wittig reaction, and double oxidative photocyclization. The photocyclization was a highly regioselective process. The molecular structures of DH-1 and DH-2 were confirmed by X-ray single-crystal analysis. Multiple intermolecular interactions, such as C-S, C-Se, S-S, S-Se, and Se-Se, were observed in the crystal packing structures of these compounds. Spectroscopic results and our previous work showed that the combination of molecular structure change and heteroatom replacement from S to Se could precisely modulate molecular energy levels.
