Syntheses and crystal structures of benzohexathia[7]helicene and naphthalene cored double helicene.

Bis(trimethylsilyl)benzohexathia[7]helicene 1, naphthalene cored double helicene 2 (the fused dimer of 1), and a novel ten-membered cyclic diketone with four moieties of dithieno[2,3-b:3',2'-d]thiophene (3) were efficiently synthesized. Their crystal structures were determined with single-crystal X-ray analysis. In their crystal packings, they all show multiple short contacts including intermolecular pi...pi, pi...S, and S...S interactions. UV/vis spectra indicate that significant pi-electron delocalization existed in 1, 2, and 3.