Viedma Ripening of Chiral Coordination Polymers Based on Achiral Molecules

Abstract

When the chiral coordination polymers were composed of achiral molecules, the deracemization of the bulk product remains a great challenge if without any chiral induction. The Viedma ripening theory was adopted herein to help the achievement of mirror symmetry breaking for the bulk chirality of two chiral coordination polymers. The enantiomeric excess of the bulk chirality for the first compound is about 100%, which means absolute asymmetric synthesis. The deracemization degree of the bulk chirality for the second compound fluctuates occasionally. Further study has discussed the different deracemization degree of the bulk chirality for two compounds with the consideration of enantioselective incorporation in crystal cluster.

Spontaneous Deracemizations

“…Ethylenediammonium sulfate was the first compound other than NaClO 3 and NaBrO 3 for which the phenomenon was detected. , To the best of our knowledge, all commercial achiral organic compounds forming racemic conglomerates tested under Viedma grinding conditions have led to deracemization and no negative results have been reported. Viedma deracemization has also been reported to occur in the case of tetrahedral and octahedral chiral transition metals , and also in the self-assembly of supramolecular structures formed by achiral coordination ligands and metal cations Reports expanding the method to chiral compounds crystallizing as racemic conglomerates by the coupling with a deracemization of the chiral compounds in solution (Figure ).…”

“…Viedma deracemization has also been reported to occur in the case of tetrahedral and octahedral chiral transition metals 187,188 and also in the self-assembly of supramolecular structures formed by achiral coordination ligands and metal cations. 189 (b) Reports expanding the method to chiral compounds crystallizing as racemic conglomerates by the coupling with a deracemization of the chiral compounds in solution (Figure 9). The theoretical proposal that Viedma deracemization should also occur in the case of enantiomorphic phases of chiral compounds racemizing in solution, 111 by virtue of the equivalence in the number of compounds and phases with the case of NaClO 3 , was soon experimentally reported.…”

Chiral Metal–Organic Frameworks

“…In other words, compared to the solution-to-homochiral crystal process proposed by Kondepudi et al, Viedma presented an absolute symmetry breaking from a conglomerate to homochiral crystal (Figure ). Since this initial report in 2005, there are currently already a handful of examples that employ Viedma ripening to transform racemic crystal mixtures to homochirality, including ionic crystals, amino acid derivatives, aromatic compounds, drug molecules, and coordination complexes. − However, the exact induction mechanism is still not fully understood. The current explanation is that the attrition enhanced Ostwald ripening (dissolution and recrystallization) cycle that amplified the chirality of the crystals.…”

“…The current explanation is that the attrition enhanced Ostwald ripening (dissolution and recrystallization) cycle that amplified the chirality of the crystals. To our knowledge, the first and, so far, the only report using the Viedma ripening approach to induce homochiral MOFs was reported in 2019 by Wu and co-workers . They chose the previous established conglomerate crystals with opposite chirality as the platform to study the availability of Viedma ripening in promoting asymmetric crystallization of CMOFs.…”

Crystallization Behavior of Heterotrinuclear ZnII–LnIII–ZnII Complexes Bearing Two Tripodal Nonadentate Ligands: Possibility for Absolute Spontaneous Resolution

“…By contrast, it is well known that ca. 5% of chiral compounds exhibit spontaneous resolution, where it is believed that equal amounts of both enantiomorphic crystals (conglomerates) are deposited. − Recently, an interesting crystallization phenomenon named total spontaneous resolution has been recognized, − in which pure (100% enantiomeric excess) one-handed enantiomorphic crystals were deposited in a crystallization experiment (Figure ) under the conditions of an attrition-enhanced resolution or rapid catalytic racemization taking place in solution. In the cases of some transition-metal or lanthanoid complexes, − no catalyst was required for this phenomenon owing to a rapid ligand-exchange process leading to racemization.…”