Making Molecular and Macromolecular Helical Tubes: Covalent and Noncovalent Approaches

Abstract

Aromatic foldamers possess well-defined cavity that can be stabilized by discrete intramolecular interactions including hydrogen bonding, solvophobicity, electrostatic repulsion, or coordination. Long foldamers can form dynamic deep helical tubular architectures that are not only structurally attractive but also useful hosts for guest encapsulation, chirality induction, delivery, and catalysis. This kind of helical tubular structures can be formed by single molecules or macromolecules or by connecting short-folded or helical segments through noncovalent or covalent forces. This perspective summarizes the recent advances on the construction of helical tubes and their properties and functions.

Nanostructured Micelle Nanotubes Self‐Assembled from Dinucleobase Monomers in Water

“…Following this bioinspired strategy,inthis work we aim at reaching ap recise control on the shape and dimensions of amphiphilic assemblies,soastobuild unique architectures in aqueous environments.I np articular,b yp rogramming an amphiphile with directional and complementary hydrogenbonding interactions,wemanaged to synthesize anovel class of helically chiral nanotubes with structurally defined pores that can be tailored with lipophilic chemical coatings (Figure 1), as in micellar architectures.I nterestingly,t his unprecedented design produced tubular structures with uniform, partially filled pores of about 2nm, which are compatible with molecular dimensions and thus allows to fill the gap between nanotubes generated through the stacking of covalent macrocycles, [4] rosettes, [5] or foldamers, [6] with typical pore diameters below 1nm, and the nanotubes assembled from classical amphiphilic molecules,w ith internal diameters exceeding 10 nm. [7] Results and Discussion…”

Polypyridine‐Based Helical Amide Foldamer Channels: Rapid Transport of Water and Protons with High Ion Rejection

“…As such, one‐pot polymerization has been pursued as a logical alternative to achieve efficient synthesis of long covalent ONTs derived from hydrogen‐bonded aromatic amide foldamers . Presumably arising from the backbone rigidity induced low reactivities of the amines and carboxylic acids, such one‐pot polymerization endeavors have so far not been successful, generating only short fully hydrogen‐bonded ONTs of average tubular lengths less than or equal to 1.1 nm .…”

“…As such, one‐pot polymerization has been pursued as a logical alternative to achieve efficient synthesis of long covalent ONTs derived from hydrogen‐bonded aromatic amide foldamers . Presumably arising from the backbone rigidity induced low reactivities of the amines and carboxylic acids, such one‐pot polymerization endeavors have so far not been successful, generating only short fully hydrogen‐bonded ONTs of average tubular lengths less than or equal to 1.1 nm . The rigidity‐induced low reactivity can be evidenced by the fact that, upon partial relaxation of the hydrogen‐bonded rigid backbone by eliminating 50 % intramolecular hydrogen bonds, the polymerized partially hydrogen‐bonded ONTs have a helical length of up to 6.1 nm .…”

Nanostructured Micelle Nanotubes Self‐Assembled from Dinucleobase Monomers in Water

“…In particular, by programming an amphiphile with directional and complementary hydrogen‐bonding interactions, we managed to synthesize a novel class of helically chiral nanotubes with structurally defined pores that can be tailored with lipophilic chemical coatings (Figure ), as in micellar architectures. Interestingly, this unprecedented design produced tubular structures with uniform, partially filled pores of about 2 nm, which are compatible with molecular dimensions and thus allows to fill the gap between nanotubes generated through the stacking of covalent macrocycles, rosettes, or foldamers, with typical pore diameters below 1 nm, and the nanotubes assembled from classical amphiphilic molecules, with internal diameters exceeding 10 nm…”