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Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid
The co-crystal of phenazine (Phz) and chloranilic acid (H(2)ca) becomes ferroelectric upon cooling through the loss of inversion symmetry. Further cooling results in the development of an incommensurate ferroelectric phase, followed by a lock-in transition towards a twofold superstructure. Here we p...
Autores principales: | , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
International Union of Crystallography
2015
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383393/ https://www.ncbi.nlm.nih.gov/pubmed/25827376 http://dx.doi.org/10.1107/S2052520615004084 |
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author | Noohinejad, Leila Mondal, Swastik Ali, Sk Imran Dey, Somnath van Smaalen, Sander Schönleber, Andreas |
author_facet | Noohinejad, Leila Mondal, Swastik Ali, Sk Imran Dey, Somnath van Smaalen, Sander Schönleber, Andreas |
author_sort | Noohinejad, Leila |
collection | PubMed |
description | The co-crystal of phenazine (Phz) and chloranilic acid (H(2)ca) becomes ferroelectric upon cooling through the loss of inversion symmetry. Further cooling results in the development of an incommensurate ferroelectric phase, followed by a lock-in transition towards a twofold superstructure. Here we present the incommensurately modulated crystal structure of Phz-H(2)ca at T = 139 K with a symmetry given by the superspace group P2(1)(½ σ(2) ½)0 and σ(2) = 0.5139. The modulation mainly affects the positions of the protons within half of the intermolecular hydrogen bonds that are responsible for the spontaneous polarization in all three low-temperature phases. Evidence for proton transfer in part of the hydrogen bonds is obtained from the correlated dependence on the phase of the modulation of the lengths of bonds involved in resonance stabilization of the acidic anion, and much smaller variations of bond lengths of atoms not involved in the resonance mechanism. Incommensurability is explained as competition between proton transfer favored for single hydrogen bonds on the basis of pK (a) values and avoiding unfavorable Coulomb repulsion within the lattice of the resulting ionic molecules. |
format | Online Article Text |
id | pubmed-4383393 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | International Union of Crystallography |
record_format | MEDLINE/PubMed |
spelling | pubmed-43833932015-04-03 Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid Noohinejad, Leila Mondal, Swastik Ali, Sk Imran Dey, Somnath van Smaalen, Sander Schönleber, Andreas Acta Crystallogr B Struct Sci Cryst Eng Mater Research Papers The co-crystal of phenazine (Phz) and chloranilic acid (H(2)ca) becomes ferroelectric upon cooling through the loss of inversion symmetry. Further cooling results in the development of an incommensurate ferroelectric phase, followed by a lock-in transition towards a twofold superstructure. Here we present the incommensurately modulated crystal structure of Phz-H(2)ca at T = 139 K with a symmetry given by the superspace group P2(1)(½ σ(2) ½)0 and σ(2) = 0.5139. The modulation mainly affects the positions of the protons within half of the intermolecular hydrogen bonds that are responsible for the spontaneous polarization in all three low-temperature phases. Evidence for proton transfer in part of the hydrogen bonds is obtained from the correlated dependence on the phase of the modulation of the lengths of bonds involved in resonance stabilization of the acidic anion, and much smaller variations of bond lengths of atoms not involved in the resonance mechanism. Incommensurability is explained as competition between proton transfer favored for single hydrogen bonds on the basis of pK (a) values and avoiding unfavorable Coulomb repulsion within the lattice of the resulting ionic molecules. International Union of Crystallography 2015-03-31 /pmc/articles/PMC4383393/ /pubmed/25827376 http://dx.doi.org/10.1107/S2052520615004084 Text en © Leila Noohinejad et al. 2015 http://creativecommons.org/licenses/by/2.0/uk/ This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited. |
spellingShingle | Research Papers Noohinejad, Leila Mondal, Swastik Ali, Sk Imran Dey, Somnath van Smaalen, Sander Schönleber, Andreas Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid |
title | Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid |
title_full | Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid |
title_fullStr | Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid |
title_full_unstemmed | Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid |
title_short | Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid |
title_sort | resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine–chloranilic acid |
topic | Research Papers |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383393/ https://www.ncbi.nlm.nih.gov/pubmed/25827376 http://dx.doi.org/10.1107/S2052520615004084 |
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