Crystal structures of 3-halo-2-organochalcogenylbenzo[b]chalcogenophenes

Abstract

The structure of the title compounds 3-bromo-2-(phenylsulfanyl)benzo[b]thiophene (C14H9BrS2; 1), 3-iodo-2-(phenylsulfanyl)benzo[b]thiophene (C14H9IS2; 2), 3-bromo-2-(phenylselanyl)benzo[b]selenophene (C14H9BrSe2; 3), and 3-iodo-2-(phenylselanyl)benzo[b]selenophene (C14H9ISe2; 4) were determined by single-crystal X-ray diffraction; all structures presented monoclinic (P21/c) symmetry. The phenyl group is distant from the halogen atom to minimize the steric hindrance repulsion for all structures. Moreover, the structures of 3 and 4 show an almost linear alignment of halogen–selenium–carbon atoms arising from the intramolecular orbital interaction between a lone pair of electrons on the halogen atom and the antibonding σ*Se–C orbital (n halogen→σ*Se–C). This interaction leads to significant differences in the three-dimensional packing of the molecules, which are assembled through π–π and C—H...π interactions. These data provide a better comprehension of the intermolecular packing in benzo[b]chalcogenophenes, which is relevant for optoelectronic applications.

Various Sorts of Chalcogen Bonds Formed by an Aromatic System

“…Moreover, the emphasis here lies with the intrinsic preferences for geometrical alignment, free of external forces such as crystal packing phenomena. Nonetheless, there are indications that perpendicular alignments of the sort representing the most stable dimers a , b , and c , as well as certain others, do appear in crystals, ,− albeit modified a bit by crystal packing forces. In a broader sense, earlier surveys of crystal structures had suggested a proclivity of nucleophiles to approach a divalent S either from directly above or within the molecular plane, consistent with the perpendicular and coplanar dimers elucidated here.…”