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The rich solid-state phase behavior of dl -aminoheptanoic acid: Five polymorphic forms and their phase transitions

The rich solid-state phase behavior of dl -aminoheptanoic acid: Five polymorphic forms and their phase transitions
The rich solid-state phase behavior of dl -aminoheptanoic acid: Five polymorphic forms and their phase transitions

The rich landscape of enantiotropically related polymorphic forms and their solid-state phase transitions of dl-2-aminoheptanoic acid (dl-AHE) has been explored using a range of complementary characterization techniques, and is largely exemplary of the polymorphic behavior of linear aliphatic amino acids. As many as five new polymorphic forms were found, connected by four fully reversible solid-state phase transitions. Two low temperature forms were refined in a high Z′ crystal structure, which is a new phenomenon for linear aliphatic amino acids. All five structures consist of two-dimensional hydrogen-bonded bilayers interconnected by weak van der Waals interactions. The single-crystal-to-single-crystal phase transitions involve shifts of bilayers and/or conformational changes in the aliphatic chain. Compared to two similar phase transitions of the related amino acid dl-norleucine, the enthalpies of transition and NMR chemical shift differences are notably smaller in dl-aminoheptanoic acid. This is explained to be a result of both the nature of the conformational changes and the increased chain length, weakening the interactions between the bilayers.

1528-7483
242-252
Smets, Mireille M.H.
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Pitak, Mateusz B.
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Cadden, Joseph
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Kip, Vincent R.
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De Wijs, Gilles A.
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Van Eck, Ernst R.H.
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Tinnemans, Paul
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Meekes, Hugo
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Vlieg, Elias
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Coles, Simon J.
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Cuppen, Herma M.
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Smets, Mireille M.H.
42b742ae-d2fd-4ae4-94bf-6c87e4e78ac3
Pitak, Mateusz B.
eeb6a00f-2291-4376-830f-d30dfd607ed1
Cadden, Joseph
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Kip, Vincent R.
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De Wijs, Gilles A.
3fbfd053-cd16-425b-acc7-9e788d381a04
Van Eck, Ernst R.H.
f93e2578-161d-4db9-9ceb-a38c1311e6a8
Tinnemans, Paul
259aa7bb-b751-4960-a836-ef6b7f37ff7e
Meekes, Hugo
2efde48e-73b4-4762-9a8c-329fb85cb4ac
Vlieg, Elias
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Coles, Simon J.
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Cuppen, Herma M.
f94d78b1-db42-4e67-b4cd-2731674aade2

Smets, Mireille M.H., Pitak, Mateusz B., Cadden, Joseph, Kip, Vincent R., De Wijs, Gilles A., Van Eck, Ernst R.H., Tinnemans, Paul, Meekes, Hugo, Vlieg, Elias, Coles, Simon J. and Cuppen, Herma M. (2018) The rich solid-state phase behavior of dl -aminoheptanoic acid: Five polymorphic forms and their phase transitions Crystal Growth & Design, 18, (1), pp. 242-252. (doi:10.1021/acs.cgd.7b01175).

Record type: Article

Abstract

The rich landscape of enantiotropically related polymorphic forms and their solid-state phase transitions of dl-2-aminoheptanoic acid (dl-AHE) has been explored using a range of complementary characterization techniques, and is largely exemplary of the polymorphic behavior of linear aliphatic amino acids. As many as five new polymorphic forms were found, connected by four fully reversible solid-state phase transitions. Two low temperature forms were refined in a high Z′ crystal structure, which is a new phenomenon for linear aliphatic amino acids. All five structures consist of two-dimensional hydrogen-bonded bilayers interconnected by weak van der Waals interactions. The single-crystal-to-single-crystal phase transitions involve shifts of bilayers and/or conformational changes in the aliphatic chain. Compared to two similar phase transitions of the related amino acid dl-norleucine, the enthalpies of transition and NMR chemical shift differences are notably smaller in dl-aminoheptanoic acid. This is explained to be a result of both the nature of the conformational changes and the increased chain length, weakening the interactions between the bilayers.

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Accepted/In Press date: 22 August 2017
e-pub ahead of print date: 29 November 2017
Published date: 3 January 2018

Identifiers

Local EPrints ID: 417413
URI: https://eprints.soton.ac.uk/id/eprint/417413
ISSN: 1528-7483
PURE UUID: c8322ac8-51ae-4fd6-8e34-13500cbb16d1
ORCID for Mateusz B. Pitak: ORCID iD orcid.org/0000-0002-3680-7100
ORCID for Simon J. Coles: ORCID iD orcid.org/0000-0001-8414-9272

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Date deposited: 31 Jan 2018 17:30
Last modified: 02 Feb 2018 17:30

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Contributors

Author: Mireille M.H. Smets
Author: Mateusz B. Pitak ORCID iD
Author: Joseph Cadden
Author: Vincent R. Kip
Author: Gilles A. De Wijs
Author: Ernst R.H. Van Eck
Author: Paul Tinnemans
Author: Hugo Meekes
Author: Elias Vlieg
Author: Simon J. Coles ORCID iD
Author: Herma M. Cuppen

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