Related Experiment Video
Updated: Oct 14, 2025
09:34
Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly
Published on: February 6, 2020
7.5K
Light-controlled interconversion between a [c2]daisy chain and a lasso-type pseudo[1]rotaxane
Chih-Wei Chu1, Daniel L Stares1, Christoph A Schalley1
1Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 20, Berlin 14195, Germany. c.schalley@fu-berlin.de.
Chemical Communications (Cambridge, England)
|November 4, 2021
Summary
This study introduces a light-responsive molecule that changes its structure between a daisy chain and a lasso form using light. This novel photoswitchable conjugate offers new possibilities in molecular machinery and supramolecular chemistry.
Area of Science:
- Supramolecular Chemistry
- Photochemistry
- Organic Chemistry
Background:
- Crown ethers and ammonium ions form host-guest complexes.
- Photoswitches enable light-controlled molecular changes.
- Arylazopyrazole derivatives are effective photoswitches.
Purpose of the Study:
- To design and synthesize a novel light-responsive conjugate.
- To investigate the structural transformation of the conjugate upon light irradiation.
- To explore the potential of this system in molecular switches and machines.
Main Methods:
- Synthesis of a crown ether/ammonium conjugate incorporating an arylazopyrazole photoswitch.
- Photoisomerization studies using UV-Vis spectroscopy and NMR.
- Structural characterization of the E- and Z-isomers.
Main Results:
- The conjugate exists as a [c2]daisy chain in the E-isomer form.
- Upon Z-isomerization of the photoswitch, the conjugate transforms into a lasso-type pseudo[1]rotaxane.
- The structural switching is reversible and light-controllable.
Conclusions:
- A light-responsive molecular system capable of reversible structural transformation was developed.
- The arylazopyrazole photoswitch effectively controls the self-assembly of the crown ether/ammonium conjugate.
- This work demonstrates a new strategy for creating light-switchable supramolecular architectures.
Related Concept Videos
01:26Photochemical Electrocyclic Reactions: Stereochemistry
1.9K
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
1.9K
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
11.0K
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
11.0K
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
3.8K
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
3.8K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.5K
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.
2.5K
01:17Thermal Electrocyclic Reactions: Stereochemistry
2.1K
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.
2.1K
01:16Cycloaddition Reactions: Overview
2.9K
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
2.9K