Saunders, LK, Pallipurath, AR orcid.org/0000-0002-9778-5160, Gutmann, MJ et al. (3 more authors) (2021) A quantum crystallographic approach to short hydrogen bonds. CrystEngComm. ISSN 1466-8033
Abstract
In this work we use high-resolution synchrotron X-ray diffraction for electron density mapping, in conjunction with ab initio modelling, to study short O—H⋯O and O+—H⋯O− hydrogen bonds whose behaviour is known to be tuneable by temperature. The short hydrogen bonds have donor–acceptor distances in the region of 2.45 Å and are formed in substituted urea and organic acid molecular complexes of N,N′-dimethylurea oxalic acid 2 : 1 (1), N,N-dimethylurea 2,4-dinitrobenzoate 1 : 1 (2) and N,N-dimethylurea 3,5-dinitrobenzoic acid 2 : 2 (3). From the combined analyses, these complexes are found to fall within the salt-cocrystal continuum and exhibit short hydrogen bonds that can be characterised as both strong and electrostatic (1, 3) or very strong with a significant covalent contribution (2). An additional charge assisted component is found to be important in distinguishing the relatively uncommon O—H⋯O pseudo-covalent interaction from a typical strong hydrogen bond. The electron density is found to be sensitive to the extent of static proton transfer, presenting it as a useful parameter in the study of the salt–cocrystal continuum. From complementary calculated hydrogen atom potentials, we attribute changes in proton position to the molecular environment. Calculated potentials also show zero barrier to proton migration, forming an ‘energy slide’ between the donor and acceptor atoms. The better fundamental understanding of the short hydrogen bond in the ‘zone of fluctuation’ presented in a salt-cocrystal continuum, enabled by studies like this, provide greater insight into their related properties and can have implications in the regulation of pharmaceutical materials.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | This journal is © The Royal Society of Chemistry 2021. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 09 Sep 2021 17:23 |
Last Modified: | 09 Sep 2021 17:23 |
Status: | Published online |
Publisher: | Royal Society of Chemistry |
Identification Number: | 10.1039/d1ce00355k |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:177990 |