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Colossal thermal expansion and negative thermal expansion in simple halogen bonded complexes

Colossal thermal expansion and negative thermal expansion in simple halogen bonded complexes
Colossal thermal expansion and negative thermal expansion in simple halogen bonded complexes
The crystal structures of the simple monoclinic halogen-bonded complexes pyridine-ICl and pyridine-IBr have been redetermined using modern X-ray and neutron diffraction techniques. The representation quadric surfaces for the thermal expansion tensor have been found to consist of a hyperboloid of one sheet. Negative thermal expansion occurs parallel to the crystallographic b axis, whilst there is colossal thermal expansion in a direction approximately parallel to the a* direction. These effects arise because of a decrease in the strength of an already weak C-H center dot center dot center dot X (X = Br, Cl) hydrogen bond with increasing temperature. The decrease in strength of the hydrogen bonding originates because of the reduction in the strength of the halogen bond formed between the nitrogen atom and the IX moiety with increasing temperature. Thus since at 298 K the I-X bonds are shorter than at 110 K, there will be a smaller partial negative charge on the X halogen at 298 K, leading to a weaker C-H center dot center dot center dot X hydrogen bond.
1466-8033
237-243
Jones, Richard H.
0b6cafaf-ce4e-4a9f-b518-69e8650d051e
Knight, Kevin S.
72d11088-c632-4869-b0eb-a5639922d288
Marshall, William G.
0787607a-2eb1-4a2a-83b7-07caa30f366a
Clews, John
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Darton, Richard J.
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Pyatt, Daniel
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Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Jones, Richard H.
0b6cafaf-ce4e-4a9f-b518-69e8650d051e
Knight, Kevin S.
72d11088-c632-4869-b0eb-a5639922d288
Marshall, William G.
0787607a-2eb1-4a2a-83b7-07caa30f366a
Clews, John
7230ebc5-255e-4f90-b27c-b752f7c13795
Darton, Richard J.
d6c37816-dfbf-492f-9826-786e1441165d
Pyatt, Daniel
5637957c-bf0c-4808-9f4d-9847b440a3b9
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5

Jones, Richard H., Knight, Kevin S., Marshall, William G., Clews, John, Darton, Richard J., Pyatt, Daniel, Coles, Simon J. and Horton, Peter N. (2014) Colossal thermal expansion and negative thermal expansion in simple halogen bonded complexes. CrystEngComm, 16 (2), 237-243. (doi:10.1039/c3ce41909f).

Record type: Article

Abstract

The crystal structures of the simple monoclinic halogen-bonded complexes pyridine-ICl and pyridine-IBr have been redetermined using modern X-ray and neutron diffraction techniques. The representation quadric surfaces for the thermal expansion tensor have been found to consist of a hyperboloid of one sheet. Negative thermal expansion occurs parallel to the crystallographic b axis, whilst there is colossal thermal expansion in a direction approximately parallel to the a* direction. These effects arise because of a decrease in the strength of an already weak C-H center dot center dot center dot X (X = Br, Cl) hydrogen bond with increasing temperature. The decrease in strength of the hydrogen bonding originates because of the reduction in the strength of the halogen bond formed between the nitrogen atom and the IX moiety with increasing temperature. Thus since at 298 K the I-X bonds are shorter than at 110 K, there will be a smaller partial negative charge on the X halogen at 298 K, leading to a weaker C-H center dot center dot center dot X hydrogen bond.

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Published date: 2014
Organisations: Aeronautics, Astronautics & Comp. Eng

Identifiers

Local EPrints ID: 362482
URI: http://eprints.soton.ac.uk/id/eprint/362482
ISSN: 1466-8033
PURE UUID: e0abd4a0-150d-4fb3-b2a4-97331f22a481
ORCID for Simon J. Coles: ORCID iD orcid.org/0000-0001-8414-9272
ORCID for Peter N. Horton: ORCID iD orcid.org/0000-0001-8886-2016

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Date deposited: 25 Feb 2014 13:53
Last modified: 18 Feb 2021 16:54

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Contributors

Author: Richard H. Jones
Author: Kevin S. Knight
Author: William G. Marshall
Author: John Clews
Author: Richard J. Darton
Author: Daniel Pyatt
Author: Simon J. Coles ORCID iD
Author: Peter N. Horton ORCID iD

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