Related Experiment Video
Updated: Jul 19, 2026
16:24
Controlling the Size, Shape and Stability of Supramolecular Polymers in Water
Published on: August 2, 2012
Supramolecular complexes of spin-labelled cyclodextrins
Victor Chechik1, Gabriela Ionita
1Department of Chemistry, University of York, Heslington, York, UK YO10 5DD. vc4@york.ac.uk
Organic & Biomolecular Chemistry
|October 13, 2006
Summary
Spin-labeled cyclodextrins (SL-CDs) reveal deviations from standard viscosity models in concentrated PEG/PPG solutions, likely due to self-aggregation. Binding strength with dendrimers increases with generation, forming supramolecular aggregates.
Area of Science:
- Supramolecular chemistry
- Polymer science
- Physical chemistry
Background:
- Spin-labeled cyclodextrins (SL-CDs) are sensitive probes for molecular interactions.
- Understanding the behavior of concentrated polymer solutions like polyethylene glycol (PEG) and polypropylene glycol (PPG) is crucial.
- Dendrimers offer unique structural properties for complexation studies.
Purpose of the Study:
- To investigate the behavior of concentrated PEG/PPG solutions using SL-CDs.
- To explore the complexation dynamics between SL-CDs and adamantane-functionalized DAB dendrimers.
- To analyze deviations from the Debye-Stokes-Einstein equation in viscous polymer solutions.
Main Methods:
- Electron Paramagnetic Resonance (EPR) spectroscopy using SL-CDs.
- Viscosity measurements of PEG/PPG solutions.
- Analysis of rotational correlation times and comparison with Debye-Stokes-Einstein and fractional Debye-Stokes-Einstein equations.
- Studying the binding of SL-CDs with different generations of DAB dendrimers.
Main Results:
- SL-CDs showed deviations from the Debye-Stokes-Einstein equation in concentrated PEG/PPG solutions, indicating self-aggregation of alkylene glycols.
- The fractional Debye-Stokes-Einstein equation provided a good fit for the observed data.
- Complexation strength between SL-CDs and DAB dendrimers increased with dendrimer generation.
- Supramolecular aggregate formation was observed for the generation 3 dendrimer at high concentrations.
Conclusions:
- Concentrated PEG/PPG solutions exhibit complex behavior beyond simple viscosity effects.
- SL-CDs are effective tools for probing supramolecular interactions and solution dynamics.
- Dendrimer generation significantly influences the binding affinity and aggregation behavior with cyclodextrin-based hosts.
More Related Videos
Related Concept Videos
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:19Complexation Equilibria: The Chelate Effect
In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
02:52Stereoisomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...