Halogen bonding-driven formation of supramolecular macrocycles and double helix

The crystal structures of three intramolecularly hydrogen bonded rigid aromatic amide derivatives,which all bear one iodine atom at one end as the donor and one pyridine unit at the other end as the acceptor, have been described to reveal the utility of halogen bonding in inducing the formation of supramolecular macrocycles. All the three compounds formed intermolecular I···N halogen bonding. For short compound 1, halogen bonding induced the formation of an extended supramolecular array. For longer folded compounds 2 and 3, halogen bonding could hold two molecules to form supramolecular macrocycles even by adopting a highly distorted, energetically less favorable conformation(for 3).Depending on the solvent for the growth of crystals, compound 3 could also gave rise to a halogen bonded supramolecular double helix.