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Surprising Chemistry of 6-Azidotetrazolo[5,1-a]phthalazine: What a purported natural product reveals about the polymorphism of explosives

Surprising Chemistry of 6-Azidotetrazolo[5,1-a]phthalazine: What a purported natural product reveals about the polymorphism of explosives
Surprising Chemistry of 6-Azidotetrazolo[5,1-a]phthalazine: What a purported natural product reveals about the polymorphism of explosives

6-Azidotetrazolo[5,1-a]phthalazine (ATPH) is a nitrogen-rich compound of surprisingly broad interest. It is purported to be a natural product, yet it is closely related to substances developed as explosives and is highly polymorphic despite having a nearly planar structure with little flexibility. Seven solid forms of ATPH have been characterized by single-crystal X-ray diffraction. The structures show diverse patterns of molecular organization, including both stacked sheets and herringbone packing. In all cases, N···N and C-H···N interactions play key roles in ensuring molecular cohesion. The high polymorphism of ATPH appears to arise in part from the ability of virtually every atom of nitrogen and hydrogen in the molecule to take part in close N···N and C-H···N contacts. As a result, adjacent molecules can adopt many different relative orientations that are energetically similar, thereby generating a polymorphic landscape with an unusually high density of potential structures. This landscape has been explored in detail by the computational prediction of crystal structures. Studying ATPH has provided insights into the field of energetic materials, where access to multiple polymorphs can be used to improve performance and clarify how it depends on molecular packing. In addition, our work with ATPH shows how valuable insights into molecular crystallization, often gleaned from statistical analyses of structural databases, can also come from in-depth empirical and theoretical studies of single compounds that show distinctive behavior.

Polymorphism, crystal structure prediction, energetic materials
0022-3263
Avila, Aaron Gabriel Nunez
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Simard, Benoit Deschenes
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Arnold, Joseph, Edward
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Morency, Mathieu
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Chartrand, Daniel
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Maris, Thierry
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Berger, Gilles
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Day, Graeme M.
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Hanessian, Stephen
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Wuest, James D.
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Avila, Aaron Gabriel Nunez
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Simard, Benoit Deschenes
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Arnold, Joseph, Edward
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Morency, Mathieu
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Chartrand, Daniel
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Maris, Thierry
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Berger, Gilles
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Day, Graeme M.
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Hanessian, Stephen
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Wuest, James D.
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Avila, Aaron Gabriel Nunez, Simard, Benoit Deschenes, Arnold, Joseph, Edward, Morency, Mathieu, Chartrand, Daniel, Maris, Thierry, Berger, Gilles, Day, Graeme M., Hanessian, Stephen and Wuest, James D. (2022) Surprising Chemistry of 6-Azidotetrazolo[5,1-a]phthalazine: What a purported natural product reveals about the polymorphism of explosives. The Journal of Organic Chemistry. (doi:10.1021/acs.joc.2c00369).

Record type: Article

Abstract

6-Azidotetrazolo[5,1-a]phthalazine (ATPH) is a nitrogen-rich compound of surprisingly broad interest. It is purported to be a natural product, yet it is closely related to substances developed as explosives and is highly polymorphic despite having a nearly planar structure with little flexibility. Seven solid forms of ATPH have been characterized by single-crystal X-ray diffraction. The structures show diverse patterns of molecular organization, including both stacked sheets and herringbone packing. In all cases, N···N and C-H···N interactions play key roles in ensuring molecular cohesion. The high polymorphism of ATPH appears to arise in part from the ability of virtually every atom of nitrogen and hydrogen in the molecule to take part in close N···N and C-H···N contacts. As a result, adjacent molecules can adopt many different relative orientations that are energetically similar, thereby generating a polymorphic landscape with an unusually high density of potential structures. This landscape has been explored in detail by the computational prediction of crystal structures. Studying ATPH has provided insights into the field of energetic materials, where access to multiple polymorphs can be used to improve performance and clarify how it depends on molecular packing. In addition, our work with ATPH shows how valuable insights into molecular crystallization, often gleaned from statistical analyses of structural databases, can also come from in-depth empirical and theoretical studies of single compounds that show distinctive behavior.

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Accepted/In Press date: 19 April 2022
Published date: 3 May 2022
Additional Information: Funding Information: J.D.W. gratefully acknowledges the financial support from the Natural Sciences and Engineering Research Council of Canada (RGPIN-2019-05469). In addition, J.D.W. thanks the Canada Foundation for Innovation (Project 30910), the Canada Research Chairs Program, and the Université de Montréal for their generous support. J.E.A. and G.M.D. thank the Air Force Office of Scientific Research for funding under award no. FA8655-20-1-7000. Through membership in the HEC Materials Chemistry Consortium, which is funded by the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom via grant EP/R029431, we used computational resources provided by the Materials and Molecular Modelling Hub, which is partially funded by EPSRC (EP/T022213). In addition, we are grateful to Dr. Michel Simard for early crystallographic investigations, Dr. Pedro M. Aguiar for his assistance in obtaining variable-temperature NMR spectra, and Dr. Samir Elouatik for helping us record Raman spectra. Publisher Copyright: © 2022 American Chemical Society.
Keywords: Polymorphism, crystal structure prediction, energetic materials

Identifiers

Local EPrints ID: 456937
URI: http://eprints.soton.ac.uk/id/eprint/456937
ISSN: 0022-3263
PURE UUID: 638450c3-1fa7-4c2f-9848-c843af506094
ORCID for Graeme M. Day: ORCID iD orcid.org/0000-0001-8396-2771

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Date deposited: 17 May 2022 16:59
Last modified: 17 Mar 2024 07:15

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Contributors

Author: Aaron Gabriel Nunez Avila
Author: Benoit Deschenes Simard
Author: Joseph, Edward Arnold
Author: Mathieu Morency
Author: Daniel Chartrand
Author: Thierry Maris
Author: Gilles Berger
Author: Graeme M. Day ORCID iD
Author: Stephen Hanessian
Author: James D. Wuest

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