Modes of Micromolar Host-Guest Binding of β-Cyclodextrin Complexes Revealed by NMR Spectroscopy in Salt Water

Multitopic supramolecular guests with finely tuned affinities toward widely explored cucurbit[n]urils (CBs) and cyclodextrins (CDs) have been recently designed and tested as functional components of advanced supramolecular systems. We employed various spacers between the adamantane cage and a cationic moiety as a tool for tuning the binding strength toward CB7 to prepare a set of model guests with K-CB7 and K beta-CD values of (0.6-5.0) x 10(10) M-1 and (0.6-2.6) x 10(6) M-1, respectively. These accessible adamantylphenyl-based binding motifs open a way toward supramolecular components with an outstanding affinity toward beta-cyclodextrin. H-1 NMR experiments performed in 30% CaCl2 /D2O at 273 K along with molecular dynamics simulations allowed us to identify two arrangements of the guest@beta-CD complexes. The approach, joining experimental and theoretical methods, provided a better understanding of the structure of cyclodextrin complexes and related molecular recognition, which is highly important for the rational design of drug delivery systems, molecular sensors and switches.

Automated summary

Multitopic supramolecular guests with finely tuned affinities towards CBs and CDs have been designed and tested as functional components of advanced supramolecular systems. The approach provided a better understanding of the structure of cyclodextrin complexes and related molecular recognition.