Unimolecular Chiral Stepping Inversion Machine

Multiple Chirality Switching of a Dye-Grafted Helical Polymer Film Driven by Acid & Base

A stimuli-responsive multiple chirality switching material, which can regulate opposed chiral absorption characteristics, has great application value in the fields of optical modulation, information storage and encryption, etc. However, due to the rareness of effective functional systems and the complexity of material structures, developing this type of material remains an insurmountable challenge. Herein, a smart polymer film with multiple chirality inversion properties was fabricated efficiently based on a newly-designed acid & base-sensitive dye-grafted helical polymer. Benefited from the cooperative effects of various weak interactions (hydrogen bonds, electrostatic interaction, etc.) under the aggregated state, this polymer film exhibited a promising acid & base-driven multiple chirality inversion property containing record switchable chiral states (up to five while the solution showed three-state switching) and good reversibility. The creative exploration of such a multiple chirality switching material can not only promote the application progress of current chiroptical regulation technology, but also provide a significant guidance for the design and synthesis of future smart chiroptical switching materials and devices.

Enantioselective Recognition of Functional Organic Molecules in Water by Biomimetic Macrocyclic Hosts

Enantioselective recognition of functional organic molecules in water is routine in nature but remains a formidable challenge for synthetic hosts. Here, we reported two pairs of chiral naphthotubes with chiral centers located in the neighborhood of the inward-directing amide groups. These naphthotubes, with a chiral twisted cavity, show highly enantioselective recognition in water to a wide scope of organic molecules (90 chiral guests). The highest enantioselectivity of 34 was achieved with neotame. Small differences between all of the noncovalent interactions shielded in the hydrophobic cavity were revealed to be responsible for the enantioselective recognition in water, which is different from the traditional views. Moreover, these hosts can differentiate the analogues of aspartame using fluorescence spectroscopy. These chiral naphthotubes have made unprecedented achievements in enantioselective recognition, providing the basis for their applications in chiral analysis and separations.

Chiroptical regulation of macrocyclic arenes with flipping-induced inversion of planar chirality

Studies on various macrocyclic arenes have received increasing attention due to their straightforward syntheses, convenient derivatization, and unique complexation properties. Represented by pillar[n]arenes, several distinctive macrocyclic arenes have recently emerged with the following characteristics: they possess a pair of enantiomeric planar chiral conformations, and interconversion between these enantiomeric conformations can be achieved through the flipping of ring units. Complexation of a chiral guest with these macrocyclic arenes will lead to a shift of the equilibrium between the Rp and Sp conformers, leading to intriguing possibilities for chiral induction and sensing. By the introduction of bulky substituents on the rims, employing rotaxanation or pseudocatenation, planar chirality could be locked, enabling the enantiomeric separation of the chiral structures. The induced or separated chiral conformers/compounds exhibit significant chiroptical properties. These macrocyclic arenes, with flipping-induced inversion of planar chirality, demonstrated intriguing chiral induction dynamics and kinetics. In this featured review, we systematically summarize the progress in chiroptical induction/regulation of these macrocyclic arenes, particularly in the fields of chiral sensing, molecular machines, molecular recognition, and assembly.