Precise Manipulation of Temperature‐Driven Chirality Switching of Molecular Universal Joints through Solvent Mixing. Issue 54 (28th August 2019)

• Record Type: Journal Article
• Authors: Fan, Chunying; Yao, Jiabin; Li, Guojuan; Guo, Cheng; Wu, Wanhua; Su, Dan; Zhong, Zhihui; Zhou, Dayang; Wang, Yuliang; Chruma, Jason J.; Yang, Cheng
• Is Part Of: Chemistry. Volume 25:Issue 54(2019)
• Page Start: 12526
• Page End: 12537
• Publication Date: 2019-08-28
• Subjects: chirality switching -- pillar[n]arenes -- solvent mixing -- supramolecular chemistry -- temperature effects; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201902676
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Three chiral bicyclic pillar[5]arene derivatives termed as molecular universal joints (MUJs), were synthesized and separated enantiomerically. These MUJs showed temperature‐driven chirality switching in certain solvents. Herein, it is demonstrated that temperature‐driven chirality switching could also be realized by mixing two miscible organic solvents, in each of which chirality inversion is not accomplishable. Additionally, solvent mixing drastically varied the inversion temperature of the MUJs, for example, from far below zero to room temperature. Moreover, the temperature‐driven Sp / Rp to Rp / Sp chirality switching direction could be reversed by the solvent mixing and it was critically controlled by the mixing ratios of the two solvents. These observations allowed precise manipulation of the chirality switching behavior of the MUJs. Such a chirality switching was ascribed to the influences of solvent and temperature on the in–out equilibrium of the side rings, which is delicately controlled by several processes, including the solvation/desolvation and the inclusion/exclusion of the side rings and solvent molecules. Crucially, the solvent mixing introduced new supramolecular processes, in particular the desolvation of solvent molecules from the mixed solvent system and the solvation of the side ring by the mixed solvent, which significantly disturbed the original in–out equilibrium of MUJs and drastically switched the entropy and enthalpy changes of conformational interconversion. Abstract : Complete control : Temperature‐driven chirality switching of three pillar[5]arene‐based molecular universal joints (MUJs) can be manipulated by mixing two organic solvents, in each of which chirality inversion does not occur. By varying the solvent ratios, the inversion temperature of the MUJs drastically changed, and the temperature‐driven Sp / Rp to Rp / Sp chirality switching direction could be critically controlled.