Related Experiment Video
Updated: Jun 21, 2026
06:15
Interactive Molecular Model Assembly with 3D Printing
Published on: August 13, 2020
Squaraine rotaxanes with boat conformation macrocycles
Na Fu1, Jeffrey M Baumes, Easwaran Arunkumar
1Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46545, USA.
The Journal of Organic Chemistry
|July 31, 2009
Summary
Mechanical encapsulation of squaraine dyes within macrocycles creates rotaxanes. This process enhances dye stability and brightness, offering a new design strategy for tuning dye properties.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Organic Chemistry
Background:
- Squaraine dyes are fluorescent but susceptible to bleaching.
- Macrocyclic compounds can encapsulate guest molecules.
- Rotaxanes are mechanically interlocked molecular architectures.
Purpose of the Study:
- To investigate the mechanical encapsulation of fluorescent squaraine dyes within tetralactam macrocycles.
- To explore how rotaxane formation influences the chemical and photochemical properties of squaraine dyes.
- To understand the conformational dynamics of macrocycles in squaraine rotaxanes.
Main Methods:
- Synthesis of squaraine rotaxanes using Leigh-type tetralactam macrocycles.
- X-ray crystallography to determine solid-state structures and conformational preferences.
- Nuclear Magnetic Resonance (NMR) spectroscopy to study solution-state dynamics and conformations.
Main Results:
- Successful formation of interlocked squaraine rotaxanes.
- Demonstrated enhancement of dye stability and a six-fold increase in brightness upon rotaxane encapsulation.
- Observed correlation between macrocycle structure (phenylene vs. isophthalamide) and conformational preference (boat vs. chair).
Conclusions:
- Mechanical encapsulation via rotaxane formation is a viable strategy to improve squaraine dye performance.
- Rotaxane structure influences macrocycle conformation and dye photophysical properties.
- This approach provides a rational design parameter for developing more stable and brighter squaraine dyes.
More Related Videos
09:22Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
Published on: February 7, 2017
10:17Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Related Concept Videos
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...
02:29Conformations of Cycloalkanes
Adolf von Baeyer attempted to explain the instabilities of small and large cycloalkane rings using the concept of angle strain — the strain caused by the deviation of bond angles from the ideal 109.5° tetrahedral value for sp3 hybridized carbons. However, while cyclopropane and cyclobutane are strained, as expected from their highly compressed bond angles, cyclopentane is more strained than predicted, and cyclohexane is virtually strain-free. Hence, Baeyer’s theory that was based on the...
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...
01:10Radical Chain-Growth Polymerization: Overview
Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...