Hydrogen Bonded Foldamers with Axial Chirality: Chiroptical Properties and Applications

Abstract

Folding phenomenon refers to the formation of a specific conformation widely featured by the intramolecular interactions, which broadly exist in biomacromolecules, and are closely related to their structures and functions. A variety of oligomeric folded molecules have been designed and synthesized, namely “foldamer”, exhibiting potentials in pharmaceutical and catalysis. Molecular folding is a promising strategy to transfer chirality from substituents to the whole skeleton, when chirality transfer, amplification, evolution, and other behaviors could be achieved. Investigating chirality using foldamer model deepens the understanding of the structure‐function correlation in biomacromolecules and expands the molecular toolbox towards chiroptical and asymmetrical chemistry. Substitutes with abundant hydrogen bonding sites conjugated to a rotatable aryl group afford a parallel β‐sheet‐like conformation, which enables the emergence and manipulation of axial chirality. This concept aims to give a brief introduction and summary of the hydrogen bonded foldamers with anchored axial chirality, by taking some recent cases as examples. Design principles, control over axial chirality and applications are also reviewed.

Ferrocene: an exotic building block for supramolecular assemblies

“…29 However, the H-bonding interactions are controlled by the particular amino acid 29 and solution conditions. 34 Apart from the amino acids, other structural moieties with complementary H-bonding capabilities can also form intramolecular associations through hydrogen bonds. 56,60,62,63 1, n ′-Fc derivatives of aromatic π-moieties generally freely rotate in solution at higher temperatures, and lowering the temperature would gradually reduce the speed of rotation and eventually freeze the rotation into syn /closed conformation favorably.…”

“…Consequently, depending on the exact molecular structure 29 and environmental conditions, 1, n ′-disubstituted Fc has the potential to be controllably switched between syn - and anti -conformations, 33 thus allowing for precise control over the supramolecular structure. 34 Additionally, the facile redox reversibility of Fc with low redox potential further enables control over these noncovalent interactions. 3 Based on these excellent features, Fc has been used as a building block for the development of a wide range of supramolecular structures such as redox responsive nanostructures, sensors, 22,24,35 host–guest inclusion complexes, 6 liquid crystals, 36 supramolecular bioorganometallics, 29,34,37 and molecular machines, 28 which have been well reviewed earlier.…”

“…34 Additionally, the facile redox reversibility of Fc with low redox potential further enables control over these noncovalent interactions. 3 Based on these excellent features, Fc has been used as a building block for the development of a wide range of supramolecular structures such as redox responsive nanostructures, sensors, 22,24,35 host–guest inclusion complexes, 6 liquid crystals, 36 supramolecular bioorganometallics, 29,34,37 and molecular machines, 28 which have been well reviewed earlier. However, elegant use of Fc as an exotic building block in developing intricate metal–organic architectures, molecular receptors, supramolecular polymers, supramolecular gels and out-of-equilibrium assembly has gained significant attention recently.…”