Controlled Folding, Motional, and Constitutional Dynamic Processes of Polyheterocyclic Molecular Strands

Abstract

General design principles have been developed for the control of the structural features of polyheterocyclic strands and their effector-modulated shape changes. Induced defined molecular motions permit designed enforcement of helical as well as linear molecular shapes. The ability of such molecular strands to bind metal cations allows the generation of coiling/uncoiling processes between helically folded and extended linear states. Large molecular motions are produced on coordination of metal ions, which may be made reversible by competition with an ancillary complexing agent and fueled by sequential acid/base neutralization energy. The introduction of hydrazone units into the strands confers upon them constitutional dynamics, whereby interconversion between different strand compositions is achieved through component exchange. These features have relevance for nanomechanical devices. We present a morphological and functional analysis of such systems developed in our laboratories.

Intrinsically Photoswitchable α/β Peptides toward Two‐State Foldamers

“…[2][3][4][5][6][7][8][9] Ty pically,afoldamer is designed to highly populate as ingle conformation. [10][11][12][13][14] To this end, an appealing potential is offered by E-Z photoisomerization of double-bond containing molecules.W ehave recently shown that incorporation of af umaramide or maleamide unit at the N-terminus of ap eptidomimetic foldamer allows this latter to exhibit afunctional response as ar esult of photoisomerization. [10][11][12][13][14] To this end, an appealing potential is offered by E-Z photoisomerization of double-bond containing molecules.W ehave recently shown that incorporation of af umaramide or maleamide unit at the N-terminus of ap eptidomimetic foldamer allows this latter to exhibit afunctional response as ar esult of photoisomerization.…”

“Breathing” Motion of a Modulable Molecular Cavity

“…Among them, catenanes and rotaxanes are well known molecular systems that are frequently used as supramolecular forces in the design of molecular devices ,. Remarkable molecular motion of molecular strands from folding to unfolding states has also been achieved using coordination/de‐coordination of metal ions …”

A Design Strategy for Single‐Stranded Helicates using Pyridine‐Hydrazone Ligands and PbII

“…α,α‐Pyridine‐hydrazones (py‐hz) are known to adopt a linear shape in solution through minimising unfavourable interactions between the neighbouring nitrogen lone pairs. Upon metal ion binding, however, the py‐hz ligands rearrange into helical shapes . The difference in conformation between the uncoordinated and coordinated states of N ‐heterocyclic hydrazone ligands has been associated with a dynamic motional behaviour in solution .…”