The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

Investigation of steric influences on hydrogen-bonding motifs in cyclic ureas by using X-ray, neutron, and computational methods

Investigation of steric influences on hydrogen-bonding motifs in cyclic ureas by using X-ray, neutron, and computational methods
Investigation of steric influences on hydrogen-bonding motifs in cyclic ureas by using X-ray, neutron, and computational methods

A series of urea-derived heterocycles, 5N-substituted hexahydro-1,3,5- triazin-2-ones, has been prepared and their structures have been determined for the first time. This family of compounds only differ in their substituent at the 5-position (which is derived from the corresponding primary amine), that is, methyl (1), ethyl (2), isopropyl (3), tert-butyl (4), benzyl (5), N,N-(diethyl)ethylamine (6), and 2-hydroxyethyl (7). The common heterocyclic core of these molecules is a cyclic urea, which has the potential to form a hydrogen-bonding tape motif that consists of self-associative R2 2(8) dimers. The results from X-ray crystallography and, where possible, Laue neutron crystallography show that the hydrogen-bonding motifs that are observed and the planarity of the hydrogen bonds appear to depend on the steric hindrance at the α-carbon atom of the N substituent. With the less-hindered substituents, methyl and ethyl, the anticipated tape motif is observed. When additional methyl groups are added onto the α-carbon atom, as in the isopropyl and tert-butyl derivatives, a different 2D hydrogen-bonding motif is observed. Despite the bulkiness of the substituents, the benzyl and N,N-(diethyl)ethylamine derivatives have methylene units at the α-carbon atom and, therefore, display the tape motif. The introduction of a competing hydrogen-bond donor/acceptor in the 2-hydroxyethyl derivative disrupts the tape motif, with a hydroxy group interrupting the N-H×××O-C interactions. The geometry around the hydrogen-bearing nitrogen atoms, whether planar or non-planar, has been confirmed for compounds 2 and 5 by using Laue neutron diffraction and rationalized by using computational methods, thus demonstrating that distortion of O-C-N-H torsion angles occurs to maintain almost-linear hydrogen-bonding interactions. The incredible bulk: A series of cyclic ureas has been studied to examine the influence of bulky substituents on the hydrogen-bonding motifs that form and the degree to which the urea group can be distorted to maintain strong intermolecular contacts.

computational chemistry, hydrogen bonds, neutron diffraction, self-assembly, supramolecular chemistry
1861-4728
2642-2651
McCormick, Laura J.
f1c2f8cd-adcc-4bbf-9289-0b33a006d2bb
McDonnell-Worth, Ciaran
9237ca3c-52b9-46e6-8e71-4815de0f5a86
Platts, James A.
2df1575c-ebd8-4dac-af9e-1590b47f0a73
Edwards, Alison J.
5ba9d596-9a31-4b76-8fdd-5209b8ca2d9a
Turner, David R.
bf5671a0-4a0a-41ed-b2f7-a539ccab65aa
McCormick, Laura J.
f1c2f8cd-adcc-4bbf-9289-0b33a006d2bb
McDonnell-Worth, Ciaran
9237ca3c-52b9-46e6-8e71-4815de0f5a86
Platts, James A.
2df1575c-ebd8-4dac-af9e-1590b47f0a73
Edwards, Alison J.
5ba9d596-9a31-4b76-8fdd-5209b8ca2d9a
Turner, David R.
bf5671a0-4a0a-41ed-b2f7-a539ccab65aa

McCormick, Laura J., McDonnell-Worth, Ciaran, Platts, James A., Edwards, Alison J. and Turner, David R. (2013) Investigation of steric influences on hydrogen-bonding motifs in cyclic ureas by using X-ray, neutron, and computational methods. Chemistry - An Asian Journal, 8 (11), 2642-2651. (doi:10.1002/asia.201300530).

Record type: Article

Abstract

A series of urea-derived heterocycles, 5N-substituted hexahydro-1,3,5- triazin-2-ones, has been prepared and their structures have been determined for the first time. This family of compounds only differ in their substituent at the 5-position (which is derived from the corresponding primary amine), that is, methyl (1), ethyl (2), isopropyl (3), tert-butyl (4), benzyl (5), N,N-(diethyl)ethylamine (6), and 2-hydroxyethyl (7). The common heterocyclic core of these molecules is a cyclic urea, which has the potential to form a hydrogen-bonding tape motif that consists of self-associative R2 2(8) dimers. The results from X-ray crystallography and, where possible, Laue neutron crystallography show that the hydrogen-bonding motifs that are observed and the planarity of the hydrogen bonds appear to depend on the steric hindrance at the α-carbon atom of the N substituent. With the less-hindered substituents, methyl and ethyl, the anticipated tape motif is observed. When additional methyl groups are added onto the α-carbon atom, as in the isopropyl and tert-butyl derivatives, a different 2D hydrogen-bonding motif is observed. Despite the bulkiness of the substituents, the benzyl and N,N-(diethyl)ethylamine derivatives have methylene units at the α-carbon atom and, therefore, display the tape motif. The introduction of a competing hydrogen-bond donor/acceptor in the 2-hydroxyethyl derivative disrupts the tape motif, with a hydroxy group interrupting the N-H×××O-C interactions. The geometry around the hydrogen-bearing nitrogen atoms, whether planar or non-planar, has been confirmed for compounds 2 and 5 by using Laue neutron diffraction and rationalized by using computational methods, thus demonstrating that distortion of O-C-N-H torsion angles occurs to maintain almost-linear hydrogen-bonding interactions. The incredible bulk: A series of cyclic ureas has been studied to examine the influence of bulky substituents on the hydrogen-bonding motifs that form and the degree to which the urea group can be distorted to maintain strong intermolecular contacts.

This record has no associated files available for download.

More information

e-pub ahead of print date: 8 August 2013
Published date: 1 November 2013
Keywords: computational chemistry, hydrogen bonds, neutron diffraction, self-assembly, supramolecular chemistry

Identifiers

Local EPrints ID: 438795
URI: http://eprints.soton.ac.uk/id/eprint/438795
ISSN: 1861-4728
PURE UUID: d665b284-3c58-46db-a5cd-8c93cbd56ff6
ORCID for Laura J. McCormick: ORCID iD orcid.org/0000-0002-6634-4717

Catalogue record

Date deposited: 24 Mar 2020 17:52
Last modified: 18 Feb 2021 17:41

Export record

Altmetrics

Contributors

Author: Ciaran McDonnell-Worth
Author: James A. Platts
Author: Alison J. Edwards
Author: David R. Turner

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×