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Resonance-stabilized partial proton transfer in hydrogen bonds of incommensurate phenazine-chloranilic acid

Title data

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.
In: Acta Crystallographica Section B. Vol. 71 (2015) . - pp. 228-234.
ISSN 2052-5206
DOI: https://doi.org/10.1107/S2052520615004084

Project information

Project financing: Deutscher Akademischer Austauschdienst

Abstract in another language

The co-crystal of phenazine (Phz) and chloranilic acid (H2ca) 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-H2ca at T = 139 K with a symmetry given by the superspace group P21(½ [sigma]2 ½)0 and [sigma]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 pKa values and avoiding unfavorable Coulomb repulsion within the lattice of the resulting ionic molecules.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: protron transfer; ferroelectric materials; incommensurate structure.
Institutions of the University: Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography > Chair Crystallography - Univ.-Prof. Dr. Sander van Smaalen
Profile Fields > Advanced Fields > Advanced Materials
Profile Fields
Profile Fields > Advanced Fields
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 500 Natural sciences
500 Science > 530 Physics
Date Deposited: 01 Dec 2016 07:59
Last Modified: 24 Feb 2017 09:34
URI: https://eref.uni-bayreuth.de/id/eprint/35232