Inversion of the Supramolecular Chirality of Nanofibrous Structures through Co‐Assembly with Achiral Molecules

Abstract

To understand the behavior of chiral nanostructures, it is of critical importance to study howa chiral molecules regulate the chirality of such nanostructures and what the main driving forces for the regulation processes are.Inthis work, the supramolecular chirality of helical nanofibers consisting of phenylalanine-based enantiomers is inverted by achiral bis-(pyridinyl) derivatives through co-assembly.T his inversion is mainly mediated by intermolecular hydrogen bonding interactions between the achiral additives and the chiral molecules, which may induce stereoselective interactions and different reorientations for the assembled molecules,a sc onfirmed by calculations.This work not only exemplifies afeasible method to invert the helicity of chiral nanostructures by the addition of achiral molecules,but also provides amethod to explore their functions in environments where chiral and achiral molecules are in close proximity.Helical and twisted nanostructures with controllable chirality are attracting attention owing to their crucial roles in the fields of catalysis, [1] sensing or recognition, [2] chiroptical switches, [3] medicine, [4] biomineralization, [5] and biology. [6] To tune the chirality of nanostructures and to influence the conformation of chiral assemblies,t he participation of chiral guests or asymmetric factors is usually required. [7] On the other hand, it has remained challenging to tune the chiral conformation (right-handed, P;l eft-handed, M)o fn anostructures by achiral molecules,b ut it is very important to have an overall understanding of the assembly mechanisms of chiral nanostructures in materials science and biology. [8] Such studies should provide complementary information on regulating the chirality of nanostructures and methods for exploring their functions when in close proximity with achiral molecules.To obtain chiral nanostructures,s upramolecular assemblies are often employed as they may self-assemble in ac ontrollable way through non-covalent interactions,s uch as hydrogen bonding, p-p stacking, and electrostatic inter-actions. [9] Thec hirality of supramolecular nanostructures is usually determined by the molecular chirality. [10] Because of the non-covalent interactions,some chiral nanostructures are successfully controlled by external stimuli, such as light, [11] temperature, [12] solvent, [13] pH, [14] rotary stirring, [15] and chiral additives, [16] leading to as o-called helix-to-helix transition between P and M.H owever,i nt hese cases,c hiral guests or asymmetric factors are always present. In fact, chiral supramolecular structures usually do not exist alone in biological or self-assembled aggregates,b ut are closely dependent on the guests around them, which can be chiral, asymmetric, or achiral. However,little is known about the helical inversion of supramolecular nanostructures triggered by achiral molecules,which is very important for understanding the origins of chirality in supramolecular systems.Inspired by the above situation, we selected phenylalanine-based e...

Coassembly Modulated pH‐Responsive Hydrogel for Dye Absorption and Release

“…Increasingly, multicomponent supramolecular gels have attracted much attention in recent years, due to the advantages of synergistic effects between individual components, which offer the potential of developing “soft” materials with highly tunable microscopic and macroscopic properties . Especially, more and more interests have highly focused on two‐component gels, which are of significant importance as particular functionalities can be easily introduced by one component that ultimately transfers these properties over the whole self‐assembled system . Furthermore, the ratio of the two components represents a parameter that can be varied to generate different morphologies and to modulate the properties of the materials .…”

Self‐Sorting Double‐Network Hydrogels with Tunable Supramolecular Handedness and Mechanical Properties

“…[8,11] Hence, the regulation of self-sorting by achiral factors in a mixture of chiral molecular building blocks with identical absolute configurational chirality (such as l-type phenylalanine-based enantiomers) is a formidable challenge, since chiral factors and asymmetric parameters have greater influence on both the chirality of assemblies and the stacking arrangement direction of building blocks than achiral factors. [9b] In our previous research, achiral factors, such as achiral additives [12] and achiral substituents, [13] were successfully utilized to tune the supramolecular chirality of hydrogels in co-/self-assembly systems. Based on these studies, we envisaged that it would be possible to distinguish helical nanostructures in the two-component hydrogel systems by monitoring the helicity and chiroptical activity, even when the mixed building blocks possessed the same configurational chirality and very similar molecular structures.…”

Chiroptical Helices of N‐Terminal Aryl Amino Acids through Orthogonal Noncovalent Interactions

“…[16][17][18][19][20][21][22] Fori nstance,F eng et al explored the influence of bipyridine in tuning the supramolecular chirality of terephthalic phenylalaine derivatives. [23] Liu and co-workers reported ap yrimidine/aryl amino acid hydrogen-bonded coassembly with emerging chiral nanostructures and chiroptical properties. [24] In spite of these developments,the construction of an integrated coassembly from ternary component systems would provide more efficient and flexible ways to manipulate the supramolecular chirality as well as chiroptical properties.…”