Recent advances in the development of the btp motif: A versatile terdentate coordination ligand for applications in supramolecular self-assembly, cation and anion recognition chemistries
Adam F. Henwood, Isabel N. Hegarty, Eoin P. McCarney, June I. Lovitt, Shauna R. Donohoe, Thorfinnur Gunnlaugsson
Abstract
The btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] ligand is a terdentate ligand that, analogously to many other terdentate ligands such as 2,2′;6,2″-terpyridine (terpy), has been shown to effectively bind to cationic metals through the central pyridyl nitrogen atom and through the triazolyl nitrogen atoms; however, in contrast to such classical ligands, btps also possess a unique capacity to bind to anions as well. Polarisation of the hydrogen atoms of the triazole rings allows them to form strong hydrogen bonding interactions with both anionic guests and with other btps through self-association. This dual binding property has seen the btp motif extended beyond traditional coordination chemistry applications to wider areas of contemporary interest, particularly in supramolecular chemistry. Thus, this review focuses initially on developments in btp coordination chemistry, discussing the use of this ligand with different metal ions, from transition metals to lanthanides and actinides. Then the second half of this review discusses ‘all-organic’ and supramolecular applications of this motif, where more unusual applications of this motif are explored, ranging from medicinal and optoelectronic applications to anion binding macrocycles and helicates, and mechanically interlocked molecules. We conclude by discussing potential future avenues of exploration for this highly exciting molecular building block.