Extremely strong tubular stacking of aromatic oligoamide macrocycles.

As the third-generation rigid macrocycles evolved from progenitor , cyclic aromatic oligoamides , with a backbone of reduced constraint, exhibit extremely strong stacking with an astoundingly high affinity (estimated lower limit of > 10 M in CHCl), which leads to dispersed tubular stacks that undergo further assembly in solution. Computational study reveals a very large binding energy (-49.77 kcal mol) and indicates highly cooperative local dipole interactions that account for the observed strength and directionality for the stacking of . In the solid-state, X-ray diffraction (XRD) confirms that the aggregation of results in well-aligned tubular stacks. The persistent tubular assemblies of , with their non-deformable sub-nm pore, are expected to possess many interesting functions. One such function, transmembrane ion transport, is observed for .