Introduction of a continuous internal hydrogen-bonding network suppressed the conformational flexibility of a series of oligoaromatic foldamers; with a lengthened backbone. The helical ordering over up to six aromatic repeating units was established in solution by a 2D NOESY study and in the solid state by an X-ray diffraction method. Computational molecular modeling further corroborates the experimentally observed helical propagation in this class of foldable molecular strands.
Persistently Folded Circular Aromatic Amide Pentamers Containing Modularly Tunable Cation-Binding Cavities with High Ion Selectivity
In this work, we illustrated a novel design strategy that allows systematically tunable interior properties (effective cavity size, steric crowdedness, and hydrophobicity) contained within a novel class of shape-persistent aromatic pentamers to take place on a scale below 3 angstrom. Such finely tunable structural features are complimented by experimentally observable functional variations in ion-binding potential. Results of the selective, differential binding affinities of three circular pentamers for Li(+), Na(+), K(+), Rb(+), and Cs(+), substantiated by metal-containing crystal structures and computational modeling, are detailed.
Crystallographic Evidence of an Unusual, Pentagon-Shaped Folding Pattern in a Circular Aromatic Pentamer
Introduction of a continuous hydrogen-bonding network suppressed the conformational flexibility of an oligomeric backbone. Cyclization of a rigidified, suitably sized oligomer led to a circular aromatic pentamer. Its crystal structure determined by X-ray crystallography reveals a pseudo five-fold symmetric planarity in the solid state, which is quite unusual among all the previously described shape-persistent macrocycles and synthetic foldamers with biased conformations enforced by noncovalent forces.
Synthesis, Structural Investigations, Hydrogen−Deuterium Exchange Studies, and Molecular Modeling of Conformationally Stablilized Aromatic Oligoamides
Biasing the conformational preferences of aromatic oligoamides by internally placing intramolecular hydrogen bonds has led to a series of stably folded molecular strands. This article presents the results from extensive solid-state, solution, and computational studies on these foldingoligomers. Depending on its backbone length, an oligoamide adopts a crescent or helical conformation. Surprisingly, despite