Self‐Assembly of a Purely Covalent Cage with Homochirality by Imine Formation in Water

Abstract

Self‐assembly of host molecules in aqueous media via metal–ligand coordination is well developed. However, the preparation of purely covalent counterparts in water has remained a formidable task. An anionic tetrahedron cage was successfully self‐assembled in a [4+4] manner by condensing a trisamine and a trisformyl in water. Even although each individual imine bond is rather labile and apt to hydrolyze in water, the tetrahedron is remarkably stable or inert due to multivalence. The tetrahedral cages, as well as its neutral counterparts dissolved in organic solvent, have homochirality, namely that their four propeller‐shaped trisformyl residues adopt the same rotational conformation. The cage is able to take advantage of hydrophobic effect to accommodate a variety of guest molecules in water. When a chiral guest was recognized, the formation of one enantiomer of the cage became more favored relative to the other. As a consequence, the cage could be produced in an enantioselective manner. The tetrahedron is able to maintain its chirality after removal of the chiral guest—probably on account of the cooperative occurrence of intramolecular forces that restrict the intramolecular flipping of phenyl units in the cage framework.

Heterochiral Diastereomer-Discriminative Diphanes That Form Hierarchical Superstructures with Nonlinear Optical Properties

“…Similarly, the negative-to-positive bisignate curve is attributed to the M -configuration of diphane (3 S ,3 S )- 3 . As compared to the previously reported single-cavity cages, 10 , 11 the value for the anisotropy factor of two chiral diphanes is relatively low ( g abs = 0.0004 at 240 nm). This low value probably results from the relatively higher symmetry of the upper and lower halves of the diphanes ( Figure 4 a, vide infra).…”

A Dioscorea opposita Thunb Polysaccharide-Based Dual-Responsive Hydrogel for Insulin Controlled Release

“…After 120 h, more than 70% of the hydrogels still remained. The degradation occurred mainly due to the hydrolysis of imines in PBS [ 40 , 41 ]. When the glucose concentration increased in the solution, the degradation rate of the hydrogel increased significantly.…”

Recognition in the Domain of Molecular Chirality: From Noncovalent Interactions to Separation of Enantiomers

“…Very recently, Li and co-authors designed and prepared homochiral self-assembled purely covalent cages through imine formation in water. 951,952 Enantioselective encapsulation of small chiral compounds was demonstrated for these cages by NMR spectroscopy and circular dichroism analyses, paving the way for their utilization for enantiomer sensing and separation. 4.5.2.…”

“…In the last decades, enantioselective sensors based on homochiral metal-organic frameworks, − chiral covalent organic frameworks, homochiral zeolites, , and nanoparticles with chiral geometrical shapes, or functionalized with chiral ligands that confer overall chirality, have been developed for enantioselective sensing of small molecules, such as antibiotics, toxins, and chemicals, biomacromolecules, such as DNA and protein, and biomarkers in living cells. Very recently, Li and co-authors designed and prepared homochiral self-assembled purely covalent cages through imine formation in water. , Enantioselective encapsulation of small chiral compounds was demonstrated for these cages by NMR spectroscopy and circular dichroism analyses, paving the way for their utilization for enantiomer sensing and separation.…”