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Published on: December 5, 2019
Toward reversible control of cucurbit[n]uril complexes
1Center for Supramolecular Science and Department of Chemistry, University of Miami , Coral Gables, Florida 33124-0431, United States.
Cucurbit[n]urils (CBn) are synthetic hosts that form highly stable complexes with guests. Researchers developed methods to reversibly control CBn binding affinity using electron and proton transfer reactions.
Area of Science:
- Supramolecular Chemistry
- Host-Guest Chemistry
- Chemical Synthesis
Background:
- Cucurbit[n]urils (CBn) are macrocyclic hosts with barrel-like structures.
- CBn hosts exhibit high binding affinities for positively charged hydrophobic guests, rivaling biological interactions.
- Their limited aqueous solubility presents challenges for some applications.
Purpose of the Study:
- To develop methods for reversible modulation of CBn host-guest binding affinity under mild conditions.
- To explore the influence of redox and proton transfer reactions on CBn complex stability.
- To investigate the binding properties of CBn with novel guest molecules, including paramagnetic species.
Main Methods:
- Complexation studies with redox-active guests (viologens, ferrocenes, cobaltoceniums).
- Investigation of proton transfer effects on binding affinity and host location.
- Binding assays with paramagnetic TEMPO-residue containing guests and CB7/CB8.
- Utilizing slow time-scale experimental techniques like NMR spectroscopy.
Main Results:
- Electron transfer reactions involving guests can be altered by CBn complexation, enabling binding control.
- Proton transfer reactions significantly impact CBn binding affinity and host positioning.
- CB7 and CB8 form exceptionally stable complexes with TEMPO-containing guests.
- Distinct microscopic complexes were observed using NMR, highlighting the stability of CBn inclusion complexes.
Conclusions:
- Reversible control over CBn binding affinity is achievable through external stimuli like electron and proton transfer.
- CBn hosts offer a versatile platform for creating highly stable, tunable supramolecular assemblies.
- The unique properties of CBn complexes open avenues for applications in molecular recognition and sensing.
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