Supramolecular 2D monolayered nanosheets constructed by using synergy of non-covalent interactions.

Here, a straightforward and rational approach to construct supramolecular assemblies with ordered nanostructures in a two-dimensional arrangement is reported. Taking advantage of the synergistic effect of multiple non-covalent interactions (hydrogen bonding and π-π interactions), the designed molecular monomer has a specific orientation in the self-assembly process, thus realizing two-dimensional control. Supramolecular two-dimensional nanosheets with single-layer thickness and controllable dimensions have been obtained, which can be clearly confirmed using TEM, SEM, AFM and XRD and by comparing with the self-assembled structures of the control system. The strategy of collaborative self-assembly proposed here using multiple non-covalent interactions is expected to be extended to the construction of various kinds of unique supramolecular 2D materials.

Foldamer-Based Potassium Channels with High Ion Selectivity and Transport Activity.

Small molecules that independently perform natural channel-like functions show greatly potential in the treatment of human diseases. Taking advantage of aromatic helical scaffolds, we develop a kind of foldamer-based ion channels with lumen size varying from 3.8 to 2.3 Å through a sequence substitution strategy. Our results clearly elucidate the importance of channel size in ion transport selectivity in molecular detail, eventually leading to the discoveries of the best artificial K+ channel by far and a rare sodium-preferential channel as well. High K+ selectivity and transport activity together make foldamers promising in therapeutic applications.

Controlling Keto-Enol Tautomerism of Ureidopyrimidinone to Generate a Single-Quadruple AADD-DDAA Dimeric Array.

Units of ureidopyrimidinone (UPy) which dimerize via strong quadruple hydrogen bonding are widely used for the construction of supramolecular systems. This self-complementary system exists in the tautomerism equilibrium of 4[1H]-pyrimidinone dimer and pyrimidin-4-ol dimer, making generated supramolecular assembly systems essentially complicated. In this contribution, a rational but simple design concept is described for preorganizing the self-complementary quadruple hydrogen bonding of UPy via supramolecular strategy into a single-quadruple DDAA-AADD dimeric array. With this concept, the designed UPy derivatives form only 4[1H]-pyrimidinone dimer with a ketone configuration via intermolecular hydrogen-bonding interactions, both in the solid state as well as in solution, as is evident from single-crystal X-ray diffraction and 1H NMR spectroscopy. The single DDAA-AADD dimeric array provides defined noncovalent driving forces that can be used to generate constitutionally clear supramolecular structures that are vitally important in the fields of supramolecular chemistry and materials.

Hybrid Helical Polymer Nanochannels Constructed by Combining Aromatic Amide and Pyridine-Oxadiazole Structural Sequences.

An effective method is reported to synthesize aromatic helical polymer nanochannels by combining both the well-studied aromatic amide helical codons with pyridine-oxadiazole helical codons into helical structure sequences. With this strategy, a type of helical polymer nanochannel that shows structure-directed transmembrane transport functions is synthesized. Although such nanochannels show relatively weak selectivity for the transportation of alkali metal ions, accessible chemical mutation of helical structure sequences will provide a great chance for the design of desired channel property. The straightforward preparation of well-established pyridine-oxadiazole helical structure will significantly promote the synthesis of this kind of aromatic helical polymer nanochannels. With the development of aromatic amide foldamers, moreover, a number of "monomers" will be available for the preparation of helical polymer nanochannels.

Highly Efficient Exclusion of Alkali Metal Ions via Electrostatic Repulsion Inside Positively Charged Channels.

Understanding of the structure-function relationships of natural protein channels remains a challenging task because of their unattainable physiological functions in terms of selectivity. To achieve this, a synthetic system of chemically modified channels has been constructed based on helical polymer scaffolds. Here, we report a type of positively charged channels in which multiple quaternary ammonium groups are covalently modified on the lumen surface of helical polymer while the helical conformation is intact. Compared to unmodified channels, the existence of multiple charged groups in the cavity not only makes the lumen size narrower but also essentially changes the channel properties without obstructing channel structure. Our study indicates that positively charged channels preferentially transport anions with size-dependent selectivity, whereas alkali metal ions are almost completely suppressed by electrostatic repulsion. As a consequence, a specific artificial channel with high Cl-/Na+ selectivity ratio of 41:1 is obtained.

Light-responsive vesicles for enantioselective release of chiral drugs prepared from a supra-amphiphilic M-helix.

A kind of light-responsive vesicle was prepared by aqueous self-assembly of α-CD and an azobenzene-containing M-helical foldamer, which displayed dynamic disassembly-reassembly structural transformation when alternately irradiated by UV and visible light. Distinctively, this vesicle also exhibited enantioselective release abilities toward racemic propranolol (a ß-blocker), owing to the M-helical building blocks.

Helical supramolecular polymer nanotubes with wide lumen for glucose transport: towards the development of functional membrane-spanning channels.

The manipulation of strong noncovalent interactions provides a concise and versatile strategy for constructing highly ordered supramolecular structures. By using a shape-persistent building block consisting of phenanthroline derivatives and two quadruply hydrogen-bonding AADD moieties, a type of precise helical supramolecular polymer (HSP) nanotube has been developed. The helical conformation of the supramolecular polymers has been proved via various techniques, showing significantly expanded topologies of supramolecular polymers. From the production of new topological structures of supramolecular polymers, predictable properties and functions have arisen. In this study, the helical folding of supramolecular polymers gave rise to the generation of specific wide lumen structures that can be directly visualized via TEM, and the resulting HSP nanotubes can puncture the lipid bilayer membrane to facilitate the transportation of glucose.

Supramolecular nanochannels self-assembled by helical pyridine-pyridazine oligomers.

Herein, we demonstrate a supramolecular nanochannel formed by intermolecular π stacking of pyridine-pyridazine helical oligomers, wherein alkali ions could be easily recognized and transported. Importantly, this nanochannel also revealed reversible collection and triggered-release behaviors via modulating the folded and unfolded states of helical pyridine-pyridazine oligomers.

A Switchable Helical Capsule for Encapsulation and Release of Potassium Ion.

A type of aromatic helical capsules was synthesized. The crystal structure proved an inner cavity that could perform switchable encapsulation and release of potassium ion through protonation/deprotonation-mediated extension and contraction of molecular motion.

Highly Selective Artificial Potassium Ion Channels Constructed from Pore-Containing Helical Oligomers.

Potassium ion channels specifically transport K+ ions over Na+ ions across a cell membrane. A queue of four binding sites in the K+ channel pore plays significant roles during highly selective conduction. A kind of aromatic helical oligomer was synthesized that can selectively bind K+ over Na+ . By aromatic stacking of helical oligomers, a type of artificial K+ channels with contiguous K+ binding sites was constructed. Such artificial channels exhibited exceptionally high K+ /Na+ selectivity ratios during transmembrane ion conduction.