A Volumetric Analysis of the 1H NMR Chemical Shielding in Supramolecular Systems.

Jiří Brus,Jiří Czernek

doi:10.3390/ijms22073333

Abstract

The liquid state NMR chemical shift of protons is a parameter frequently used to characterize host–guest complexes. Its theoretical counterpart, that is, the 1H NMR chemical shielding affected by the solvent (1H CS), may provide important insights into spatial arrangements of supramolecular systems, and it can also be reliably obtained for challenging cases of an aggregation of aromatic and antiaromatic molecules in solution. This computational analysis is performed for the complex of coronene and an antiaromatic model compound in acetonitrile by employing the GIAO-B3LYP-PCM approach combined with a saturated basis set. Predicted 1H CS values are used to generate volumetric data, whose properties are thoroughly investigated. The 1H CS isosurface, corresponding to a value of the proton chemical shift taken from a previous experimental study, is described. The presence of the 1H CS isosurface should be taken into account in deriving structural information about supramolecular hosts and their encapsulation of small molecules.

Highlights

Our method is based on the statistical evaluation of similarity measures between experimental chemical shifts, δX and δY, and permutations of the corresponding chemical shieldings, σX and σY, in an investigated system of nuclei X and
Using data from the solid-state NMR measurements and from calculations of crystalline structures, this method was applied in a number of “NMR crystallography” studies, as noted by Hodgkinson in the most recent review [19]
We tested various combinations of the density-functional theory (DFT) functionals with atomic-orbital basis sets and with a treatment of the solvent in order to find the computational strategy for an accurate representation of solution 2D

Summary

Introduction

Mol. Recently, significant progress was achieved in various areas of supramolecular chemistry, as exemplified by the review articles published in 2020 [1,2,3,4]. Significant progress was achieved in various areas of supramolecular chemistry, as exemplified by the review articles published in 2020 [1,2,3,4] This progress has already led to numerous applications (see an extensive survey in reference [5]) and to the preparation of a number of fascinating architectures like, for example, an enantiopure “Russian doll” [6], a triple-stranded mesocate [7], and a cage compound that can be transformed into the covalent organic framework [8]. The proton NMR chemical shift in solution is usually the most important 1 H NMR parameter because its value for the investigated hydrogen(s) in a guest molecule generally differs between encapsulated and bulk states, allowing a straightforward analysis of the guest binding and exchange [10]

Methods

Results

Conclusion