Self‐Discriminating Termination of Chiral Supramolecular Polymerization: Tuning the Length of Nanofibers

Abstract

Directing the supramolecular polymerization towards ap referred type of organization is extremely important in the design of functional soft materials.Proposed herein is asimple methodology to tune the length and optical chirality of supramolecular polymers formed from ac hiral bichromophoric binaphthalene by the control of enantiomeric excess (ee). The enantiopure compound gave thin fibers longer than afew microns,while the racemic mixture favored the formation of nanoparticles.T he thermodynamic study unveils that the heterochiral assembly gets preference over the homochiral assembly.T he stronger heterochiral binding over homochiral one terminated the elongation of fibrous assembly,thus leading to ac ontrol over the length of fibers in the nonracemic mixtures.T he supramolecular polymerization driven by p-p interactions highlights the effect of the geometry of atwisted pcore on this self-sorting assembly.The past two decades have witnessed increased attention in the field of the self-assembly of small molecules into complex architectures. [1] This interest in supramolecular polymers formed by noncovalent interactions arises mainly because of a) the desire to mimic life systems so as to understand the process of self-assembly in biological macromolecules [2a] and b) the ability to build nanostructures for practical applications by utilizing ab ottom-up approach. [2b-d] Theb ottom-up approach drives the formation of supramolecular aggregates through acombined effect of different noncovalent intermolecular forces,thus leading to complex superstructures,often possessing af ibrous nature. [3] Molecules possessing chiral centers act as building blocks for the fabrication of helical nanostructures,wherein the supramolecular chirality is determined by the chirality at the molecular level. [4,5] The fascinating structural features of different chiral nanostructures,s uch as helices,n anotapes,a nd nanotubes have attracted great interest because of their resemblance to biological structures [6a] and possible applications in chiral sensing and catalysis. [6b-d] Thep erformance of functional organic materials in optoelectronic devices is largely dependent on the organization of molecular components. [6] Hence,d irecting the selfassembly towards ap referred type of organization is an extremely important step in the design of such materials. Recently,w er eported the self-assembly of chiral binaphthalenes,b earing two perylene bis(imide) (PBI) units (1; Scheme 1), [7] into dissimilar morphologies depending on the solvent system. [8] They formed helical fibers through p-p stacking interactions in methylcyclohexane (MCH), but formed spherical aggregates in chloroform at high concentration. [8] Thef ibrous assemblies gave superior chiroptical properties,including circularly polarized luminescence (CPL) relative to the spherical aggregates.I nt he present work, we introduce an ew methodology to control the length of the fibers through the mixing of enantiomers possessing the opposite chirality.I nt his regard, earlier i...

Helical supramolecular polymers with rationally designed binding sites for chiral guest recognition

“…21) 32,[47][48][49][50][51] . Furthermore, we confirmed that the polymers of 1•2 S and 1•2 R were also immiscible [28][29][30][31][32] , which was proved by the linear change of CD intensity with changing the ratio of 1•2 S and of 1•2 R in their mixture (1•2 S :1•2 R = 100:0-0:100; Supplementary Fig. 22a), together with the fact that the elongation temperatures of enantiopure samples (1•2 S :1•2 R = 100:0 and 1•2 S :1•2 R = 0:100; T e = 335 K for both) were notably higher than that of a racemic sample (1•2 S :1•2 R = 50:50; T e = 315 K) ( Supplementary Fig.…”

“…The key to this achievement is our strategy of using the non-covalent interaction sites in the supramolecular polymer not only for the connection of the monomers but also for the recognition of chiral guests. that similar enantio-separation ability should reside in all reported supramolecular polymers that are formed via homochiral polymerization [28][29][30][31][32] , but has never been investigated. Speaking not only chirality recognition but general molecular recognition, all supramolecular polymers with self-sorting nature also potentially have the similar separation ability [47][48][49][50][51] .…”

“…Our strategy is very simple, to use the non-covalent interaction sites in the supramolecular polymer not only for the connection of monomers, but also for the recognition of chiral guest molecules. This idea has not been extensively studied but seems reasonable, because some supramolecular polymers are formed via homochiral polymerization [28][29][30][31][32] , where the elongating polymers selectively accommodate the monomers with the same chirality as their constituents. To use this stereoselective process for the enantio-separation of chiral molecules, we designed a family of helical supramolecular polymers, whose monomer is composed of an achiral main body (dendritic carboxylic acid 1; Fig.…”

Dimensional Control and Morphological Transformations of Supramolecular Polymeric Nanofibers Based on Cofacially-Stacked Planar Amphiphilic Platinum(II) Complexes

“…The latter are of widespread importance as means of accessing polymers with chain length control, narrow length dispersities, and also complex architectures such as block and star copolymers. 1,[11][12][13][14][15][16][17][18] Crystallization is also a nucleation-elongation/growth process 19 and the solution self-assembly of block copolymers (BCPs) with a crystallizable core-forming block has received…”

Inversion of Supramolecular Chirality by Sonication-Induced Organogelation

“…Instead, it is regulated by how the molecules are arranged in the self-assembled aggregates. Although various types of gelators have been shown to possess supramolecular chirality 23 24 25 26 , to date, very few peptide-based systems have been reported. For example, opposite supramolecular chirality (left- and right-handed) from porphyrin-conjugated pentapeptides in two different solvent systems were investigated by Jiang et al 27 .…”