Related Experiment Video
Updated: Aug 6, 2026
09:48
Construction and Operation of a Light-driven Gold Nanorod Rotary Motor System
Published on: June 30, 2018
Force-Induced Control of Circularly Polarized Luminescence With Rotaxane Architecture
Keigo Nonaka1, Takumi Kuroda1, Kota Masuda1
1Department of Materials Science and Engineering, Institute of Science Tokyo, Meguro-ku, Tokyo, Japan.
Angewandte Chemie (International Ed. in English)
|July 25, 2026
Summary
This study demonstrates the first mechanical control of circularly polarized luminescence (CPL) using rotaxane mechanophores. Force applied to a gel switches CPL on and off at the single-molecule level.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Chiroptical Spectroscopy
Background:
- Mechanically interlocked molecules (MIMs) enable stimuli-responsive functions.
- Previous MIM research focused on pH or chemical triggers for circularly polarized luminescence (CPL) switching.
- Mechanical control of CPL using MIMs has not been previously demonstrated.
Purpose of the Study:
- To develop a rotaxane-based mechanophore for force-induced CPL on/off switching.
- To integrate this mechanophore into a double-network (DN) gel for macroscopic force transduction.
- To establish a method for measuring mechanical CPL switching in soft materials.
Main Methods:
- Design and synthesis of a rotaxane mechanophore with a CPL-active helicene and a quencher.
- Covalent incorporation of rotaxane mechanophores into the cross-linking points of a DN gel.
- Induction of force via macroscopic swelling and shrinking of the DN gel, monitored by CPL changes.
Main Results:
- The rotaxane mechanophore exhibited reversible force-induced CPL on/off switching.
- The DN gel system allowed for force transduction from macroscopic deformation to molecular motion.
- Isotropic swelling of the gel minimized orientation artifacts, enabling accurate single-chiral emitter CPL detection.
Conclusions:
- This work presents the first demonstration of mechanical control over CPL at the single-molecule level.
- The developed rotaxane mechanophore and DN gel system offer a robust platform for studying force-induced chiroptical switching.
- This provides a new avenue for designing advanced responsive soft materials.
Related Concept Videos
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
02:11Conformations of Cyclohexane
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
02:02Chair Conformation of Cyclohexane
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
01:34Woodward–Hoffmann Selection Rules and Microscopic Reversibility
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...