A Pair of Interconverting Cages Formed from Achiral Precursors Spontaneously Resolve into Homochiral Conformers

Abstract

Without chiral induction the emergence of homochirality from achiral molecules is rather serendipitous, as the rationale is somewhat ambiguous. We herein provide a plausible solution. From achiral precursors are formed a pair of interconverting cage conformers that exhibit a C 3 -axis as the only symmetry element. When their interconversion is impeded with intramolecular H-bonding, each conformer self-sorts into a homochiral crystal, which is driven by a helical network of multivalent intermolecular interactions during the self-assembly of homochiral cage conformers. As no chiral induction is involved throughout, we believe our study could enlighten the rational design for the emergence of homochirality with several criteria: 1) formation of a molecule without inversion center or mirror plane; 2) suppression of the enantiomeric interconversion, and introduction of multivalent interactions along the helical trajectory of screw symmetry within the resulting superstructure.

Spontaneous Symmetry Breaking of Achiral Molecules Leading to the Formation of Homochiral Superstructures that Exhibit Mechanoluminescence

“…In addition, the perfluorophenyl and pyrenyl motifs of each FPy molecule are located on the same side of the flexible linker, adopting a chiral cis ‐conformation. Around the crystallographic b ‐axis, each FPy molecule rotates by 180° with respect to another, so that they are packed in a head‐to‐tail manner along the helical trajectory, forming a chiral supramolecular 2 1 ‐helix, in line with our previously proposed strategy of “ go with the flow ” [10b] . The helices are extended on the ac plane to afford the chiral polar monoclinic crystalline phase (Figure S9).…”

“…Given over 60 % of noncentrosymmetric crystals (41/65 Sohncke space groups) exhibit screw symmetry, we recently proposed a strategy that favors spontaneous chiral resolution of racemic molecules, which we termed “go with the flow” : [10b] When rational molecular design facilitates the exerting of multivalent intermolecular interactions along the helical trajectory of screw symmetry of the molecular packing, the racemates could experience narcissistic self‐sorting during crystallization, leading to the formation of homochiral conglomerates. We also applied this strategy to a series of achiral D−A molecules [10a] .…”

Molecular Face-Rotating Polyhedra: Chiral Cages Inspired by Mathematics

“…The synthesis of chiral molecular cages typically embraces two major approaches. The first one involves the use of chiral building blocks as integral components of the resulting polyhedra, such as edges, vertices, or faces, therefore imparting their chirality to the overall structure. − The other strategy entails organizing achiral components in a way that disrupts mirror and inversion symmetries, lending to chiral polyhedral structures. , Developing new forms of chiral molecular cages is crucial for advancing our understanding of chiral assembly processes, investigating molecular chirality properties, and expanding the range of applications for chiral cages.…”

Chiral Molecular Cage with Tunable Stereoinversion Barriers

“…Racemization, , a common phenomenon in dynamic stereochemistry, is a macroscopically irreversible process showing the evolution of enantiopure compounds into their corresponding racemic mixtures. Whereas racemization processes of small organic molecules, e.g., amino acids, − axially chiral compounds, − and inherently chiral molecules with Gaussian curvatures, − have been extensively investigated (Figure A), probing dynamic chirality at a supramolecular level − can be more challenging owing to the nontrivial chiral resolution process involved. Understanding the racemization kinetics and pathways of (supra)­molecular assemblies is crucial for harnessing their dynamic chirality and enabling the conversion of racemic mixtures into enantiopure compounds without using conventional enantioselective separation techniques. , …”