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Updated: May 24, 2025
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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
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Halogen Bond Strength in Solids Quantified via Zeeman-Perturbed Nuclear Quadrupole Resonance Spectroscopy.
Alireza Nari1, Mubassira Rahman1, Patrick M J Szell1
1Department of Chemistry and Biomolecular Sciences, Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada.
Journal of the American Chemical Society
|March 4, 2025
Summary
Zeeman-perturbed nuclear quadrupole resonance (Zp-NQR) spectroscopy enables the study of halogen bonds (XB) in solids. This new method quantifies XB strength using electric field gradients, correlating with interaction energies.
Area of Science:
- Solid-state chemistry
- Spectroscopy
- Materials science
Background:
- Proton Nuclear Magnetic Resonance (NMR) is standard for hydrogen bonds.
- 127I NMR is ineffective for strong halogen bond (XB) donors due to high quadrupolar coupling constants (CQ).
Purpose of the Study:
- To develop and demonstrate an innovative spectroscopic method for analyzing strong halogen bonds in solid materials.
- To quantify the strength of halogen bonds using nuclear quadrupole resonance.
Main Methods:
- Implementation of Zeeman-perturbed nuclear quadrupole resonance (Zp-NQR) spectroscopy with adjustable magnetic fields.
- Analysis of 127I and 79Br nuclei in solid powders using Zeeman-quadrupolar Hamiltonian diagonalization.
- Relativistic Density Functional Theory (DFT) computations for interaction energies.
Main Results:
- Successful acquisition and analysis of Zp-NQR spectra for 27 halogen-bonded cocrystals.
- Determination of CQ values and quadrupolar asymmetry parameters, overcoming NMR and NQR limitations.
- Strong correlations found between spectral data, structural features, and DFT-computed interaction energies.
Conclusions:
- The electric field gradient at the XB donor site is a reliable metric for quantifying XB strength in solids.
- Zp-NQR is a versatile technique applicable to diverse chemical and materials science problems.
- Halogen bond interaction energies in the studied systems range from approximately 5 to 10 kcal mol-1.
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