Crystal engineering in the gem-alkynol family: interplay between strong and weak interactions in structures of 2,3,5,6-tetrahalo[F,Cl,Br]-trans-1,4-diethynylcyclohexa-2,5-diene-1,4-diols

Abstract

Structures of the title compounds are all mediated by strong cooperative arrangements of O—H...O hydrogen bonds, supported by a variety of weaker interactions which affect the type of O—H...O synthon that is formed. The tetrafluoro compound contains hexameric O—H...O synthons in a supramolecular chair conformation, together with C≡C—H...F interactions. However, the tetrachloro and tetrabromo compounds both form tetrameric O—H...O synthons. This dominant pattern is supported by halogen...halogen interactions having one C—Cl[Br]...Cl[Br] angle close to 180° and the other close to 90°, and by C≡C—H...Cl[Br] interactions.