Aakeröy, Christer B.Panikkattu, SheeluChopade, Prashant D.Desper, John2013-02-182013-02-182012-12-17http://hdl.handle.net/2097/15308In order to study the structure-directing competition between hydrogen- and alogen-bond donors we have synthesized two ligands, 3,3’-azobipyridine and 4,4’-azobipyridine, and co-crystallized them with a series of bi-functional donor molecules comprising an activated halogen-bond donor (I or Br) as well as a hydrogen-bond donor (acid, phenol or oxime) on the same backbone. Based on the subsequent single-crystal analysis, 5 of 6 co-crystals of 3,3’-azobipyridine are assembled using hydrogen bonds as the primary driving force accompanied by weaker secondary (C-X...O) interactions. However, in 5 out of the 6 co-crystals of 4,4’-azobipyridine, both hydrogen bonds (O-H...N) and halogen bonds (C-X...N) are present as structure-directing interactions leading to 1-D chains. Since the charges on the acceptor sites in 3,3’-and 4,4’-azobipyridine are very similar, the observed difference in binding behaviour highlights the importance of binding-site location on the acceptor molecules (anti-parallel in 3,3’-azobipyridine and co-linear in 4,4’-azobipyridine) as a direct influence over the structural balance between hydrogen- and halogen-bond donors.en-USThis Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).Hydrogen-bondHalogen-bondCrystal engineeringSupramolecular chemistryAzopyridinesArticle (author version)