Effect of Halogen Bonding on Chiral Assemblies of Achiral Sulfonamide Molecules in the Crystalline Phase
Shoko Kikkawa, Misaki Okayasu, Hidemasa Hikawa, Isao Azumaya
Abstract
We investigated the relationship between the proportion of achiral compounds that crystallize as chiral crystals and how halogen bonds affect the molecular assemblies in the crystals. In addition, we evaluated the influence of halogen bonding on chiral crystallization. The systematic analysis of 76 crystal structures of secondary aromatic sulfonamides bearing halogen substituents (F, Cl, Br, and I) on the benzene rings revealed that two kinds of intermolecular interactions play significant roles in the chiral or achiral assembly of molecules in their crystals: strong hydrogen bonds (NH···O) and weak halogen bonds (halogen···halogen, halogen···O, halogen···π, aromatic···aromatic, and halogen···H). The proportion of compounds that showed chiral crystallization among the halogenated compounds was lower (2.6%) than that of the non-halogenated sulfonamides (11%). Thus, there is a correlation between the kind of contacts and the chirality of the assembly of adjacent molecules. In particular, the proportion of chiral crystallization was reduced by aromatic···aromatic contacts and increased by Br···O or Br···π contacts.