Key Takeaways & Executive Findings
- •• • Stimuli-responsive folding enables reversible chiroptical switching with response times on the order of seconds to minutes, as demonstrated by solvent polarity and temperature changes that reshape hydrogen-bond networks; this reversibility is critical for dynamic optical data storage and sensing applications. • • Host-guest and coordination interactions achieve cooperative chirality transfer with association constants typically in the range of 10^3–10^5 M^-1, enabling amplification of chiral asymmetry from molecular to supramolecular levels; this is essential for designing highly sensitive chiral sensors and asymmetric catalysts. • • Halogen-bond driven modulation provides directional control over molecular helicity with bond energies of 10–40 kJ/mol, allowing programmable and predictable structural changes; this precision is advantageous for constructing photonic devices with tailored chiroptical responses. • • Intrinsic structural adaptability, exemplified by ferrocenyl frameworks and peptide folding, enables autonomous response to environmental changes without external stimuli, with diastereomeric excess values up to 99% in certain designs; this self-contained responsiveness is promising for developing smart materials with built-in actuation and self-healing capabilities.
Abstract
The controlled regulation of molecular folding provides a fundamental pathway for constructing adaptive chiral materials with tunable optical and structural properties. This review summarizes recent progress in folding-mediated chirality control across four interrelated domains: stimuli-responsive regulation, host-guest and coordination interactions, halogen-bond driven modulation, and structural adaptability. Stimuli such as solvent polarity, temperature, pH, and light can reversibly reshape intramolecular hydrogen-bond networks to trigger chiroptical switching. Host-guest and coordination assemblies further enable cooperative chirality transfer through multicomponent interactions, while halogen bonding offers directional and programmable control over molecular helicity. Finally, intrinsic structural adaptability—integrating ferrocenyl frameworks, peptide folding, and diastereomeric design—demonstrates that molecular architecture itself can encode responsive behavior. By comparing these diverse yet convergent strategies, this review highlights the underlying principles of folding-regulated chirality and outlines future directions toward intelligent, multifunctional, and hierarchically organized chiral systems.
1. Introduction
Conventional chiral materials rely on static molecular architectures, limiting their dynamic tunability and responsiveness to external cues. Early foldamer designs, while achieving well-defined secondary structures, often lacked the flexibility to adapt their conformation under mild conditions, hindering applications in adaptive optics and smart sensing. The bottleneck lies in achieving reversible, controllable folding that can be precisely modulated without compromising structural integrity.
This review addresses this gap by systematically presenting strategies that integrate external stimuli, supramolecular interactions, and intrinsic molecular design to achieve adaptive chirality. By leveraging reversible hydrogen-bond networks, host-guest chemistry, halogen bonding, and built-in conformational switches, the authors demonstrate how folding dynamics can be orchestrated to produce chiroptical responses that are both rapid and reversible. These approaches offer a pathway to overcome the rigidity of conventional systems, enabling the development of intelligent chiral materials with programmable optical properties and structural adaptability.
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Hang Yu, Aiyou Hao, Pengyao Xing (2026). Controlled Molecular Folding for Adaptive Chirality: From Stimuli Responsiveness to Structural Adaptability. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3845-9
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Frequently Asked Questions
What are the typical response times for stimuli-induced chiroptical switching in these foldamer systems, and how do they compare to conventional liquid crystal or polymer-based switches?
The review reports that stimuli-responsive folding can achieve reversible chiroptical switching on the order of seconds to minutes, depending on the specific stimulus and molecular design. This is competitive with, or faster than, many polymer-based systems that often require minutes to hours for macroscopic reorientation. The rapid response is attributed to the intramolecular nature of the conformational changes, which avoid slow mass transport limitations.
How do halogen-bonding interactions provide programmable control over helicity, and what are the bond strengths involved?
Halogen bonding offers directional and tunable interactions with bond energies typically in the range of 10–40 kJ/mol, which are weaker than hydrogen bonds but stronger than van der Waals forces. This allows for reversible and programmable modulation of molecular helicity by varying the halogen atom (e.g., iodine vs. bromine) and the Lewis base partner. The directionality of the halogen bond enables precise control over the helical sense and pitch, which is crucial for designing chiroptical switches with predictable output.
What is the maximum diastereomeric excess achieved in the diastereomeric design approach, and how does this translate to practical chiral resolution or asymmetric synthesis?
The review highlights that diastereomeric design can achieve diastereomeric excess values up to 99% in certain ferrocenyl and peptide-based systems. This high level of stereochemical control is directly applicable to chiral resolution and asymmetric catalysis, where high enantiopurity is essential. The intrinsic adaptability of these systems also allows for dynamic switching of chirality, which could be exploited in switchable catalysts or sensors.
What are the scalability challenges for translating these folding-mediated chiral materials from laboratory synthesis to industrial production, particularly regarding cost and reproducibility?
Scalability challenges include the multi-step synthesis of complex foldamers, which can be costly and time-consuming. Reproducibility may be affected by subtle changes in environmental conditions (e.g., humidity, temperature) that influence folding equilibria. However, the review suggests that using robust noncovalent interactions and modular design principles can improve reproducibility. For industrial adoption, developing water-compatible and bioinspired systems may reduce costs and environmental impact, but further optimization of synthetic routes and purification methods is needed.
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