Emergence and Amplification of Chirality via Achiral–Chiral Polymorphic Transformation in Sodium Chlorate Solution Growth

Abstract

Chiral symmetry breaking during the chiral crystallization from a sodium chlorate (NaClO3) aqueous solution is an intriguing phenomenon because it provides insights into the prebiotic process of biohomochirality. However, a mechanism of the emergence and amplification of chirality remains controversial, especially for crystallization from highly supersaturated solution, and one of the hypotheses proposed before is a transition toward the homochiral state during the early stages of crystallization. In this contribution, we directly examined the early stage of crystallization by in situ polarized-light microscopy. The observation revealed that achiral crystals, which appear prior to the formation of chiral crystals, transform to the chiral crystal through two kinds of polymorphic transformations: (1) martensitic transformation (MT) and (2) solution-mediated phase transition (SMPT). The SMPT is remarkably facilitated by contact with a chiral crystal. Notably, the resulting enantiomorph through contact-facilitated SMPT is strongly directed by the contacting enantiomorph. In contrast, the MT yields two enantiomorphs in equal probability. The emergence and amplification of chirality has generally been considered to be a result of direct nucleation of a chiral crystal and its fragmentation. In contrast, our observations provide a possibility that the MT and contact-facilitated SMPT play a role for the emergence and amplification of chirality, respectively.

Plasmonic Manipulation of Sodium Chlorate Chiral Crystallization: Directed Chirality Transfer via Contact-Induced Polymorphic Transformation and Formation of Liquid Precursor

“…NaClO 3 was used as the target compound to crystallize. NaClO 3 is known to crystallize in two kinds of polymorphic forms from an aqueous solution: (i) a monoclinic achiral metastable phase with a P 2 1 / a space group ,, and (ii) a cubic chiral stable phase with a P 2 1 3 space group . The solubility of the achiral metastable phase is ∼1.6 times higher than that of the chiral stable phase .…”

Crystal characterization and transformation of the forms I and II of anticoagulant drug rivaroxaban

“…Their kinetics may be generally affected by the solid structure, imperfections within the solid structure, particle size and sample history . Solution‐mediated phase transformations typically occur through exposure to liquid and comprise three essential steps: (i) dissolution of a metastable phase, (ii) nucleate of a more stable phase, and (iii) growth of the stable phase . The above three steps are all dependent on some operating factors, such as temperature, solvent, slurry density, stirring speed, seeding, impurity, and so on .…”

Plasmonic Manipulation-Controlled Chiral Crystallization of Sodium Chlorate

“…The orbital angular momentum generates the mechanical torque, which directly acts on the surface of the metastable crystal (Figure b). Precisely, the direction of orbital angular momentum effects the direction of the asymmetrical distortion of the octahedral structure of sodium ions in the achiral crystal, , which determines the handedness of the resultant chiral crystal (Figure c). It is noteworthy that the spatial mismatch between the rotational torque and structural strain of NaClO 3 is sufficiently large.…”