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

Abstract

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 β‑CD values of (0.6–5.0) × 1010 M–1 and (0.6–2.6) × 106 M–1, respectively. These accessible adamantylphenyl-based binding motifs open a way toward supramolecular components with an outstanding affinity toward β-cyclodextrin. 1H NMR experiments performed in 30% CaCl2/D2O at 273 K along with molecular dynamics simulations allowed us to identify two arrangements of the guest@β-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.

Adamantane-Substituted Purine Nucleosides: Synthesis, Host–Guest Complexes with β-Cyclodextrin and Biological Activity

“…We observed clear complexation-induced shifts (CIS) of 0.10 ppm, 0.07, and −0.10 ppm for the adamantane bridgehead H(e) atoms and aromatic H(b) and H(c) atoms, respectively. The downfield shift of adamantane signals is well recognized as an indication of the inclusion of the adamantane moiety into the β-CD cavity [ 47 , 48 ]. In addition, we performed a 2D 1 H- 1 H ROESY experiment on the equimolar mixture of 24 and β-CD.…”

Integration of a bulky adamantane unit with 9-phenyl-9H-3,9′-bicarbazole: a novel host design for solution-processed narrowband TADF-OLEDs

“…Compounds 1, 5, and 7 were synthesized using a previously reported procedure. [30][31][32] Synthesis of 4-((1s,3s)-adamantan-1-yl)aniline (2). Compound 1 (15.4 g, 0.06 mol) and platinum on carbon (Pt/C) were combined in a round-bottom flask containing dried ethyl acetate (200 mL).…”

Nuclear Magnetic Resonance

“…130 Host À guest binding of b-cyclodextrin complexes was revealed by experimental NMR spectroscopy and supported by GIAO NMR calculations using the DFT approach. 131…”