Narcissistic self-sorting in anion-coordination-driven assemblies

Understanding multicomponent low molecular weight gels from gelators to networks

BACKGROUND

The construction of gels from low molecular weight gelators (LMWG) has been extensively studied in the fields of bio-nanotechnology and other fields. However, the understanding gaps still prevent the prediction of LMWG from the full design of those gel systems. Gels with multicomponent become even more complicated because of the multiple interference effects coexist in the composite gel systems.

AIM OF REVIEW

This review emphasizes systems view on the understanding of multicomponent low molecular weight gels (MLMWGs), and summarizes recent progress on the construction of desired networks of MLMWGs, including self-sorting and co-assembly, as well as the challenges and approaches to understanding MLMWGs, with the hope that the opportunities from natural products and peptides can speed up the understanding process and close the gaps between the design and prediction of structures.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review is focused on three key concepts. Firstly, understanding the complicated multicomponent gels systems requires a systems perspective on MLMWGs. Secondly, several protocols can be applied to control self-sorting and co-assembly behaviors in those multicomponent gels system, including the certain complementary structures, chirality inducing and dynamic control. Thirdly, the discussion is anchored in challenges and strategies of understanding MLMWGs, and some examples are provided for the understanding of multicomponent gels constructed from small natural products and subtle designed short peptides.

Triamine and Tetramine Edge-Length Matching Drives Heteroleptic Triangular and Tetragonal Prism Assembly

Heteroleptic metal-organic capsules, which incorporate more than one type of ligand, can provide enclosed, anisotropic interior cavities for binding low-symmetry molecules of biological and industrial importance. However, the selective self-assembly of a single mixed-ligand architecture, as opposed to the numerous other possible self-assembly outcomes, remains a challenge. Here, we develop a design strategy for the subcomponent self-assembly of heteroleptic metal-organic architectures with anisotropic internal void spaces. Zn6Tet3Tri2 triangular prismatic and Zn8Tet2Tet'4 tetragonal prismatic architectures were prepared through careful matching of the side lengths of the tritopic (Tri) or tetratopic (Tet, Tet') and panels.

Anion-Coordination-Driven Assembly: From Discrete Supramolecular Self-Assemblies to Functional Soft Materials

Anion templated assembly of supramolecular systems has been extensively explored in previous reports, whereas anions serve only as an auxiliary and spectator role. With the development of anion coordination chemistry in recent years, anion coordination-driven assembly (ACDA) has emerged as a new strategy for the construction of supramolecular self-assemblies. Anions are proved to exist as the main actors in the construction of supramolecular architectures, i. e., serve as the coordination center. This Review will focus on the recent progress in anion-coordination-driven assembly of discrete supramolecular architectures, such as helicates, polyhedrons and polygons, and the various applications of 'aniono'-systems. At the end of this Review, we highlight current challenges and opportunities for future research of anion-coordination-driven self-assembly.

Three modes of interactions between anions and phenolic macrocycles: a comparative study

Macrocyclic polyphenolic compounds such as resorcin[4]arenes can be considered as multidentate anion receptors. In the current work, we combine new experimental data and reports from the previous literature (solution data and deposited crystal structures from the CCDC) to systematically analyze binding motifs between resorcin[4]arene derivatives and anions, determine the role of supporting interactions from CH donors, ion pairing and estimate their relative strength. We have found that in medium polarity solvents (THF) anion binding is a main driving force for the formation of complexes between resorcinarenes and Alk₄NX salts. Three binding modes have been detected using ¹H NMR and DOSY, depending on the type of additional interactions. Mode I was observed for upper-rim unsubstituted resorcinarenes, which use OH groups and aromatic CH from the upper rim as hydrogen bond donors to form multidentate and multivalent binding sites at the upper rim. Mode II was observed for upper-rim halogenated resorcinarenes (tetrabromo- and tetraiodo-derivatives), which use OH groups and aliphatic CH atoms from the bridges to support the chelation of anions between aromatic units. This binding mode is also multidentate and multivalent, but weaker and more anion-selective than mode I (works effectively for chlorides but not for bromides). For O-substituted derivatives, mode III is observed, with anions bound in a nest formed by aromatic CH atoms in the lower rim (multidentate but monovalent binding). The relative strength of these three binding modes, their solvent-dependence, and emergence in the crystal structures (CCDC) have been evaluated.

Narcissistic Self-Sorting of Amphiphilic Collagen-Inspired Peptides in Supramolecular Vesicular Assembly

Herein, we describe the hierarchical self-assembly accompanying self-sorting of collagen-inspired peptides (CPs). The two amphiphilic CPs used in this study contained an azobenzene (Az) moiety at the N-terminal, connected through a flexible spacer, but with different lengths of the (Gly-Pro-Hyp)_n triplet (n = 5 and 7). When the CP aqueous solution (60 °C) was cooled to 4 °C, both CPs formed a triple helix structure and the pre-organized helices subsequently self-assembled into highly ordered vesicles with a diameter of 50-200 nm. Interestingly, narcissistic self-sorting was observed in both triple helix- and matured vesicle-formation processes, when the two CPs were mixed. Owing to the difference in the propensity for triple helix formation with temperature, the two CPs discriminate each other in response to a temperature change and form two kinds of triple helix foldamers, each containing a single component. The resulting differences in the amphiphilic balance and molecular length between the foldamers appear to allow individual self-sorting to form distinct vesicles. Furthermore, such vesicular assemblies were found to disassemble upon UV irradiation via trans-cis isomerization of the Az-groups. These findings offer important insights into the design of new complex but ordered, peptide self-assembly systems with potential applications in nanobiotechnology.

Synthesis and characterisation of an integratively self-sorted [Fe4L6]8+ tetrahedron

Exclusive formation of an integratively sorted tetrahedral complex enables incorporating a unique vertex.

Kinetically controlled narcissistic self-sorting of Pd(II)-linked self-assemblies from structurally similar tritopic ligands

Although many examples of self-sorting have been reported, self-sorting of structurally similar building blocks is potentially difficult. Herein, we present the narcissistic self-sorted state from two kinds of structurally similar...

A Hydrogen-Bonded Ravel Assembled by Anion Coordination

Anion-coordination-driven assembly (ACDA) is showing increasing power in the construction of anionic supramolecular architectures. Herein, by expanding the anion centers from oxoanion (phosphate or sulfate) to organic tris-carboxylates, an Archimedean solid (truncated tetrahedron) and a highly entangled, double-walled tetrahedron featuring a ravel topology have been assembled with tris-bis(urea) ligands. The results demonstrate the promising ability of tris-carboxylates as new anion coordination centers in constructing novel topologies with increasing complexity and diversity compared to phosphate or sulfate ions on account of the modifiable size and easy functionalization character of these organic anions.

Self-sorting behavior in supramolecular fullerene polymerization directed by host-guest complexation between calix[5]arene and C60

We describe self-sorting supramolecular polymerization that uses chiral calix[5]arene hosts and a dumbbell-shaped fullerene guest. In a solution containing the racemic host and the guest, the (S)-host and the (R)-host preferably formed their homomeric complexes to form helical supramolecular fullerene polymers in a self-sorting manner. The self-sorting behavior has been studied using diffusion-ordered ¹H NMR (DOSY) and circular dichroism (CD) studies. The present findings show that it is possible to accomplish controlled supramolecular polymerization.