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  1. Helical aromatic oligoamide foldamers provide negative cavities that strongly bind dicationic guests, giving complexes as stable pseudofoldaxanes with few precedents.

     
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    Free, publicly-accessible full text available May 10, 2024
  2. As a major class of foldamers, aromatic oligoamide foldamers have attracted intense interest. The rigidity of aromatic residues and amide linkages allows the development of foldamers with readily predictable, stable conformations. Aromatic oligoamide foldamers having backbones fully constrained by intramolecular hydrogen bonds have attracted wide attention. Depending on their lengths, such foldamers adopt crescent or helical conformations with highly negative inner cavities. Cyclizing the backbone of the aromatic oligoamides affords the corresponding macrocycles which are characterised by persistent shapes and non-deformable inner cavities. With their defined, inner cavities, such aromatic oligoamide foldamers and macrocycles have served as hosts for cationic and polar guests, and as transmembrane channels for transporting ions and molecules. Recent synthetic progress resulted in the construction of multi-turn hollow helices that offer three-dimensional inner pores with adjustable depth. Reducing the number of backbone-constraining hydrogen bonds leads to oligoamides which, with their partially constrained backbones, undergo either solvent- or guest-dependent folding. One class of such aromatic olgioamide foldamders, which offer multiple backbone amide NH groups as hydrogen-bond donors, are designed to bind anions with adjustable affinities. 
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  3. New aromatic oligoamide macrocycles with C 3 -symmetry bind a bipyridinium guest (G) to form compact pseudo[3]rotaxanes involving interesting enthalpic and entropic contributions. The observed high stabilities and strong positive binding cooperativity are found in few other host–guest systems. 
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  4. Abstract

    Cooperativity plays a critical role in self‐assembly and molecular recognition. A rigid aromatic oligoamide macrocycle with a cyclodirectional backbone binds with DABCO‐based cationic guests in a 2 : 1 ratio in high affinities (Ktotal≈1013 M−2) in the highly polar DMF. The host–guest binding also exhibits exceptionally strong positive cooperativity quantified by interaction factors α that are among the largest for synthetic host–guest systems. The unusually strong positive cooperativity, revealed by isothermal titration calorimetry (ITC) and fully corroborated by mass spectrometry, NMR and computational studies, is driven by guest‐induced stacking of the macrocycles and stabilization from the alkyl end chains of the guests, interactions that appear upon binding the second macrocycle. With its tight binding driven by extraordinary positive cooperativity, this host–guest system provides a tunable platform for studying molecular interactions and for constructing stable supramolecular assemblies.

     
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  5. Abstract

    Cooperativity plays a critical role in self‐assembly and molecular recognition. A rigid aromatic oligoamide macrocycle with a cyclodirectional backbone binds with DABCO‐based cationic guests in a 2 : 1 ratio in high affinities (Ktotal≈1013 M−2) in the highly polar DMF. The host–guest binding also exhibits exceptionally strong positive cooperativity quantified by interaction factors α that are among the largest for synthetic host–guest systems. The unusually strong positive cooperativity, revealed by isothermal titration calorimetry (ITC) and fully corroborated by mass spectrometry, NMR and computational studies, is driven by guest‐induced stacking of the macrocycles and stabilization from the alkyl end chains of the guests, interactions that appear upon binding the second macrocycle. With its tight binding driven by extraordinary positive cooperativity, this host–guest system provides a tunable platform for studying molecular interactions and for constructing stable supramolecular assemblies.

     
    more » « less