Covalency of hydrogen bonds in liquid water can be probed by proton nuclear magnetic resonance experiments.

Hossam Elgabarty,Thomas D Kühne,Rustam Z Khaliullin

doi:10.1038/ncomms9318

Hossam Elgabarty, Thomas D Kühne + Show 1 more

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https://doi.org/10.1038/ncomms9318

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Abstract

The concept of covalency is widely used to describe the nature of intermolecular bonds, to explain their spectroscopic features and to rationalize their chemical behaviour. Unfortunately, the degree of covalency of an intermolecular bond cannot be directly measured in an experiment. Here we established a simple quantitative relationship between the calculated covalency of hydrogen bonds in liquid water and the anisotropy of the proton magnetic shielding tensor that can be measured experimentally. This relationship enabled us to quantify the degree of covalency of hydrogen bonds in liquid water using the experimentally measured anisotropy. We estimated that the amount of electron density transferred between molecules is on the order of 10 m while the stabilization energy due to this charge transfer is ∼15 kJ mol−1. The physical insight into the fundamental nature of hydrogen bonding provided in this work will facilitate new studies of intermolecular bonding in a variety of molecular systems.

Highlights

The concept of covalency is widely used to describe the nature of intermolecular bonds, to explain their spectroscopic features and to rationalize their chemical behaviour
We reveal a quantitative relationship between the calculated components of the 1H magnetic shielding tensor and the degree of covalency of hydrogen bonds (HBs) in liquid water[19,20]
To quantify the strength of covalent interactions in a HB, we employed the decomposition analysis for condensed phase systems based on absolutely localized molecular orbitals (ALMO DA)[21,22] within Kohn–Sham density functional theory[23]

Summary

Introduction

The concept of covalency is widely used to describe the nature of intermolecular bonds, to explain their spectroscopic features and to rationalize their chemical behaviour. We established a simple quantitative relationship between the calculated covalency of hydrogen bonds in liquid water and the anisotropy of the proton magnetic shielding tensor that can be measured experimentally. We reveal a quantitative relationship between the calculated components of the 1H magnetic shielding tensor and the degree of covalency of HBs in liquid water[19,20]. Similar to various other unmeasurable auxiliary concepts (for example, wave function in quantum mechanics), covalency is a fundamental, theoretically well defined and physically meaningful quantity that is widely used by chemists to investigate the nature of intermolecular bonding. It is widely accepted that donor–acceptor interactions between molecules in liquid water affect its directly measurable structural, spectroscopic and chemical properties

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