Issue 41, 2023

NMR exchange dynamics studies of metal-capped cyclodextrins reveal multiple populations of host–guest complexes in solution

Abstract

Metal-capped molecular hosts are unique in supramolecular chemistry, benefitting from the inner cavity's hydrophobic nature and the metal center's electrochemical properties. It is shown here that the paramagnetic properties of the metals in lanthanide-capped cyclodextrins (Ln-α-CDs and Ln-β-CDs) are a convenient NMR indicator for different populations of host–guest complexes in a given solution. The paramagnetic guest exchange saturation transfer (paraGEST) method was used to study the exchange dynamics in systems composed of Ln-α-CDs or Ln-β-CDs with fluorinated guests, revealing multiple co-existing populations of host-guest complexes exclusively in solutions containing Ln-β-CDs. The enhanced spectral resolution of paraGEST, achieved by a strong pseudo contact shift induction, revealed that different molecular guests can adopt multiple orientations within Ln-β-CDs' cavities and, in contrast, only a single orientation inside Ln-α-CDs. Thus, paraGEST, which can significantly improve NMR detectability and spectral resolution of host-guest systems that experience fast exchange dynamics, is a convenient tool for studying supramolecular systems of metal-capped molecular hosts.

Graphical abstract: NMR exchange dynamics studies of metal-capped cyclodextrins reveal multiple populations of host–guest complexes in solution

Supplementary files

Article information

Article type
Edge Article
Submitted
14 jul 2023
Accepted
04 sep 2023
First published
07 sep 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2023,14, 11351-11358

NMR exchange dynamics studies of metal-capped cyclodextrins reveal multiple populations of host–guest complexes in solution

E. Goren, M. A. Iron, Y. Diskin-Posner, A. Falkovich, L. Avram and A. Bar-Shir, Chem. Sci., 2023, 14, 11351 DOI: 10.1039/D3SC03630H

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