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Urotropin azelate: a rather unwilling co-crystal

Bonin, Michel; Welberry, Thomas; Hostettler, Marc; Gardon, Manuel; Birkedal, Henrik; Chapuis, Gervais; Mockli, Pedro; Ogle, Craig; Schenk, Kurt J

Description

Urotropin (U) and azelaic acid (AA) form 1:1 co-crystals (UA) that give rise to a rather complex diffraction pattern, the main features of which are diffuse rods and-bands in addition to the Bragg reflections. UA is characterized by solvent inclusions, parasite phases, and high vacancy and dislocation densities. These defects compounded, with the pronounced tendency of U to escape from the crystal edifice lead to at least seven exotic phase transitions (many of. which barely manifest themselves...[Show more]

dc.contributor.authorBonin, Michel
dc.contributor.authorWelberry, Thomas
dc.contributor.authorHostettler, Marc
dc.contributor.authorGardon, Manuel
dc.contributor.authorBirkedal, Henrik
dc.contributor.authorChapuis, Gervais
dc.contributor.authorMockli, Pedro
dc.contributor.authorOgle, Craig
dc.contributor.authorSchenk, Kurt J
dc.date.accessioned2015-12-13T23:12:24Z
dc.date.available2015-12-13T23:12:24Z
dc.identifier.issn0108-7681
dc.identifier.urihttp://hdl.handle.net/1885/88044
dc.description.abstractUrotropin (U) and azelaic acid (AA) form 1:1 co-crystals (UA) that give rise to a rather complex diffraction pattern, the main features of which are diffuse rods and-bands in addition to the Bragg reflections. UA is characterized by solvent inclusions, parasite phases, and high vacancy and dislocation densities. These defects compounded, with the pronounced tendency of U to escape from the crystal edifice lead to at least seven exotic phase transitions (many of. which barely manifest themselves in a differential scanning calorimetry trace). These involve different incommensurate phases and a peritectoid reaction in the recrystallization regime. (Th, > 0.6). The system may be understood as an OD (order-disorder) structure based on a layer with layer group P(c)c2 and cell ao ≃ 4.7, b ≃ 26.1 and c ≃ 14.4 Å. At 338 K the layer stacking is. random, but with decreasing temperature the build-up of an orthorhombic MDO (maximal degree of order) structure with cell a1 = 2ao, b1 = b, c1 = c and space group Pcc2 is begun (at ∼301 K). The superposition structure of the OD system at T = 286 (1) K with space group Bmmb and cell a = 2ao, b = b and c = c/2 owes its cohesion to van der Waals interactions between the AA chains and to three types of hydrogen bonds of varied strength between U-U and U-AA. Before reaching completion, this MDO structure is transformed, at 282 K, into a monoclinic one with cell am = -ao + c/4, bm = b, cm = -2(ao + c/2), space group P21/c, spontaneous deformation ∼2°, and ferroelastic domains. This transformation is achieved in two steps: first a furtive triggering transition, which is not yet fully understood, and second an improper ferroelastic transition. At ∼233 K, the system reaches its ground state (cell aM = am, bM = b, cM = cm. and space group P21/c) via an irreversible transition. The phase transitions below 338 K are described by a model based on the interaction of two thermally activated slip systems. The OD structure is described in terms of a three-dimensional Monte Carlo model that involves first- and second-neighbour interactions along the a axis and first-neighbour interactions along the b and c axes. This model includes random shifts of the chains along their axes and satisfactorily accounts for most features that are seen in the observed diffraction pattern.
dc.publisherMunksgaard International Publishers
dc.sourceActa Crystallographica Section B: Structural Science
dc.subjectKeywords: Crystal structure; Densitometers; Energy conversion; Magnetic domains; Molecular spectroscopy; Monte Carlo methods; Optical materials; Phase transitions; Recrystallization (metallurgy); Azelaic acid; Ferroelastic domains; Parasite phases; Quasi spherical
dc.titleUrotropin azelate: a rather unwilling co-crystal
dc.typeJournal article
local.description.notesImported from ARIES
local.description.refereedYes
local.identifier.citationvolume59
dc.date.issued2003
local.identifier.absfor030606 - Structural Chemistry and Spectroscopy
local.identifier.absfor030505 - Physical Organic Chemistry
local.identifier.ariespublicationMigratedxPub17555
local.type.statusPublished Version
local.contributor.affiliationBonin, Michel, University of Lausanne
local.contributor.affiliationWelberry, Thomas, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationHostettler, Marc, University of Lausanne
local.contributor.affiliationGardon, Manuel, University of Lausanne
local.contributor.affiliationBirkedal, Henrik, University of Lausanne
local.contributor.affiliationChapuis, Gervais, Swiss Federal Institute of Technology (ETH)
local.contributor.affiliationMockli, Pedro, Swiss Federal Institute of Technology (ETH)
local.contributor.affiliationOgle, Craig, University of North Carolina
local.contributor.affiliationSchenk, Kurt J, University of Lausanne
local.bibliographicCitation.startpage72
local.bibliographicCitation.lastpage86
local.identifier.doi10.1107/S0108768102022164
dc.date.updated2015-12-12T08:31:28Z
local.identifier.scopusID2-s2.0-2442682905
CollectionsANU Research Publications

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