Single-Atom Tuning of Pyridine-Strapped Pillar[5]arene Capsules for Specific Guest Binding.

Pyridine bis(carboxamide)-strapped pillar[5]arene capsules were synthesized with the serendipitous formation of macrotricyclic products. The structural integrity of the supramolecular capsules, determined by the specific orientation of a single nitrogen atom, controls the electronic properties of the confined binding cavity, facilitating length-selective recognition of aliphatic organic guests with nitrile, isocyanide, and amine functional groups with exceptional host-guest binding affinity and selectivity for 1,2-diaminoethane ( > 10 M) in a polar organic solvent.