One brilliant saga we are well familiar with is that French chemist Louis Pasteur managed to manually separate the racemic mixture of single crystals of ammonium sodium tartrate tetrahydrate with tweezers in 1848 by carefully discerning the discrepancies in their morphologies. This groundbreaking experiment stands as the first artificial chiral resolution in the annals of science and technology, laying the cornerstone for what we now call stereochemistry. However,the direct impact of molecular chirality on the overall properties and functionalities of crystal , readily observable to the naked eye, has seldom beentreated as a distinct inquirybut merits contemplation.Recently,the researchers in Prof. Xinhua Wan’s Labfrom the College of Chemistry and Molecular Engineering, Peking University, conceived a novel dynamic molecular system based on the racemic mixture of asparagine monohydrate. When heated at specific faces, crystals consisting of the opposite enantiomers jump macroscopically toward the opposite directions, which could be further utilized to achieve the mechanical separation of the racemic mixtures. This significant contributionhas been published in Journal of the American Chemical Society, entitled "Directional Crystal Jumping Controlled by Chirality" (J. Am. Chem. Soc. 2024, 146, 9679-9687). Dr. Yifu Chen from the College of Chemistry and Molecular Engineering, Peking University is the first author, Prof. Xinhua Wan is the corresponding author of this work.
Schematic representations of Louis Pasteur’s manual separation experiment in 1848 and the finding about directional crystal jumping controlled by chirality in the present work.
In the present cases, a pair of enantiomeric crystals of asparagine monohydrate demonstrate opposite jump directions when subjected to thermal stimuli targeting their specific crystal faces. The hydrogen-bonded networks between asparagine molecules in a specific direction provide oriented channels for the escape of water molecules during the dehydration. The pathways for the escape of water molecules in pairs of enantiomeric crystals are fully mirrored, providing a basis for the oriented movement of these crystals. The new findings lay the foundation for the future creation of directed actuation systems based on dynamic crystals.
From a broader perspective, the relevance between chirality and motion is one of the most intriguing issues in the scientific community. Life is chiral. Living organisms, encompassing animals, plants, and microorganisms, all exhibit inherent chirality within their external structural composition, and their behavioral functions and motion patterns also possess chiral bias, such as the prevalent right-handedness in human actions and the common left-handedness in chimpanzees and monkeys. The chirality-based motion control strategy proposed in this work will not only propel the advancement of artificial chemical systems toward a more lifelike and natural direction, but also inspire an in-depth exploration of the origins of the chirality in biological functions.
This work was financially supported by the National Natural Science Foundation of China (52333008), the special funding from China Postdoctoral Science Foundation (2023TQ0005), and the National Science Foundation of Beijing City (2244091). Dr. Yifu Chen additionally acknowledges the funding of Boya Postdoctoral Fellowship at Peking Universityand the National Funding Program for Postdoctoral Researchers (GZC20230031).
Link to this work:
Yifu Chen, Jiaxing Zhang, Jie Zhang, and Xinhua Wan*, Directional Crystal Jumping Controlled by Chirality, J. Am. Chem. Soc. 2024, 146, 14, 9679-9687.
https://pubs.acs.org/doi/10.1021/jacs.3c13416
