NMR and computational studies of ammonium ion binding to dibenzo-18-crown-6

0571664 - MBÚ 2024 RIV US eng J - Journal Article
Shope, B. - Magers, D. B. - Pelczer, I. - Řeha, David - Minofar, Babak - Carey, Jannette
NMR and computational studies of ammonium ion binding to dibenzo-18-crown-6.
Structural Chemistry. Roč. 34, č. 2 (2023), s. 713-722. ISSN 1040-0400. E-ISSN 1572-9001
Institutional support: RVO:61388971
Keywords : Host-guest systems * Ligand-binding affinity * Forward and reverse titration * Molar ratio of binding * Stoichiometric titration * Conformational transitions * Synergy of experiment and computation
OECD category: Microbiology
Impact factor: 1.7, year: 2022
Method of publishing: Limited access
https://link.springer.com/article/10.1007/s11224-022-02017-8

Dibenzo-18-crown-6 (DB18C6) is a single-crown ether that can act as a host for a guest ion. In an effort to illuminate the relationships among structure, dynamics, and thermodynamics of ligand binding in a simple model for understanding the affinity and specificity of ligand interactions, nuclear magnetic resonance (NMR) experiments and density functional theory (DFT) were used to study the interaction of DB18C6 with ammonium ion. H-1-NMR was used to follow the titration of DB18C6 with ammonium chloride in deuterated methanol, a solvent chosen for its amphipathic character. Ammonium ion binds strongly to DB18C6 with a dissociation equilibrium constant at least as low as similar to 10(-6) M. DFT calculations were used to identify optimized conformations of bound and free DB18C6 and to estimate its binding energy with ammonium ion in implicit solvent. An approach is described that accounts for geometry relaxation in addition to solvation correction and basis set superposition error, to our knowledge, this is the first such report that includes the energy difference from optimizing species geometry. The lowest-energy conformer of free DB18C6 in implicit methanol acquires an open, W-shaped structure that is also the lowest-energy conformer found for the DB18C6-ammonium ion complex. These results form a foundation for further studies of this system by molecular dynamics simulations.
Permanent Link: https://hdl.handle.net/11104/0343186