Building Shape-Persistent Arylene Ethynylene Macrocycles as Scaffolds for 1,4-Diiodobutadiyne.

Two shape-persistent arylene ethynylene macrocycles have been designed and synthesized as scaffolds to bind the nonpolar molecule 1,4-diiodobutadiyne. Binding via halogen bonding interactions between the pyridine moieties of the macrocycle and 1,4-diiodobutadiyne is predicted by density functional theory calculations and has been demonstrated in solution by 13C NMR titrations. The binding constant for the macrocycle-monomer complex (K = 10.5 L mol-1) is much larger than for other comparable halogen bonds, strongly supporting cooperative binding of both ends of the diyne. These results demonstrate a fully inserted geometry of 1,4-diiodobutadiyne in the complex.