A series of compounds forming polar crystals and showing single-crystal-to-single-crystal transitions between polar phases

Centore, Roberto; Jazbinšek, Mojca; Tuzi, Angela; Roviello, Antonio; Capobianco, Amedeo; Peluso, Andrea

doi:10.1039/c2ce06352b

Cited by 48 publications

(80 citation statements)

References 46 publications

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“…Also, during the reversible phase transition, II ↔ III (both ways), crystals exhibited a jumping behaviour, although somewhat weaker than during the phase transition I to II. This is in contrast to previously reported behaviour [50] and the new model for jumping crystal phenomenon in this system has to be proposed. [51] A possible explanation of the thermosalient phenomenon may lie in the fact that a change of mutual positions of the molecules due to the change of temperature induced a severe stress in the crystal.…”

Section: Thermosalient Crystalscontrasting

confidence: 46%

“…It was also reported that during the irreversible phase transition from I to II, the polar axis undergoes a strong compression (approximately 15 %) and a single crystal of the phase I is violently shuttered into single crystal fragments of the phase II (without jumping), while in the reversible phase transition III to II the polar axis expands (approximately 14 %) and the integrity of the single crystals is preserved -and no movement of crystals was observed. [50] Our recent study ( Figures 13. and 14.) showed a different behaviour. [51] During the irreversible phase transition from I to II some of the crystals did indeed shutter into smaller fragments, but a large number remained intact and showed a typical jumping behaviour [49] -jumping all around over large distances (several cm).…”

Section: Thermosalient Crystalsmentioning

confidence: 99%

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Contemporary Diffraction Methods in Study of Polycrystals

Popović¹,

Tonejc²,

Skoko³

2015

Croat. Chem. Acta

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Diffraction in the polycrystal/crystalline powder is one of the most powerful techniques in study of microstructure and crystal structure of solids. This technique enables, in synergy with microscopic, spectroscopic and other physical techniques, a complete analysis of onephase and multi-phase substances, that are important in scientific and technological fields. Information on microstructure and crystal structure of a substance is stored in its diffraction pattern; in order to reveal this information, the diffraction pattern should be decoded by application of adequate mathematical and physical procedures which may often be rather complex. During the last decades, diffraction techniques in the polycrystal are developing rapidly due to the introduction of sophisticated instrumentation, powerful computers and by application of synchrotron radiation. This advance enables the collection and interpretation of diffraction data in a short real time as well as the study of time-resolved dynamic processes in the crystalline substance. Possibilities of diffraction techniques in the polycrystal are concisely described and illustrated by examples of authors' scientific studies.Keywords: X-ray diffraction, microstructure, crystal structure, recent advancement in diffraction. DIFFRACTION IN THE POLYCRYSTALIFFRACTION is a phenomenon in which the beam of X-rays, electrons or neutrons, by passing through a single crystal or a polycrystal, deviates from the initial direction due to the scattering on the structural motifs (atoms, ions, molecules) in the crystal. The scattered waves give rise to diffraction maxima in a set of discrete space directions due to their mutual constructive interference. These directions strongly depend on the periodicity and symmetry of the crystal. The set of diffraction maxima represent the diffraction pattern of the single crystal / polycrystal. The intensities of diffraction maxima depend on the nature of structural motifs and their mutual space arrangement. Therefore, diffraction techniques are ideal in the study of the crystal structure and microstructure: space periodicity in the crystal, unit-cell parameters (unit-cell edges a, b and c and angles among them, α, β and γ), symmetry elements which determine the space group, space periodical arrangement of structural motifs, identification of particular atoms and their coordinates, definition of the nature and length of their mutual chemical bonds, the angles among the chemical bonds, the size and shape of crystallites, distribution of crystallite sizes, the nature of the crystallite / grain boundary, stresses and strains inside the crystallite, point, planar and volume defects inside the crystallite, phase transitions in a given substance and the definition of its phase diagram, etc.In determination of the crystal structure, diffraction in the single crystal has an advantage in relation to the diffraction in the polycrystal. That is a consequence of the fact that the 3D data, obtained by diffraction in the single crystal, are transferred ...

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Section: Thermosalient Crystalscontrasting

confidence: 46%

Section: Thermosalient Crystalsmentioning

confidence: 99%

Contemporary Diffraction Methods in Study of Polycrystals

Popović¹,

Tonejc²,

Skoko³

2015

Croat. Chem. Acta

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“…The properties such as ferroelectricity, piezoelectricity, and second-order optical nonlinearlity are allowed in a noncentrosymmetric structure. Other noncentrosymmetric SCSC transitions have been previously reported [14]. We discuss a possible mechanism for the enantiomorphic SCSC phase transition based on the crystal structure changes between the α-and β-forms.…”

Section: Resultsmentioning

confidence: 99%

“…The compound enol-(S)-1 was synthesized according to the literature procedure [14]. Single crystals were obtained by slow evaporation of the solution in 2-propanol at room temperature within several days.…”

Section: Methodsmentioning

confidence: 99%

Reversible Single-Crystal-to-Single-Crystal Phase Transition of Chiral Salicylidenephenylethylamine

et al. 2016

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Abstract:The chiral crystal of enantiomeric (S)-N-3,5-di-tert-butylsalicylidene-1-phenylethylamine in the enol form [enol-(S)-1] undergoes a reversible single-crystal-to-single-crystal (SCSC) phase transition at T c ≈ 3 • C from the room temperature α-form in orthorhombic space group P2 1 2 1 2 1 (Z = 1) to the low temperature β-form in the monoclinic space group P2 1 (Z = 2) with a thermal hysteresis of approximately 1.7 • C. A detailed comparison of the crystal structures of the α-and β-forms revealed that the 5-tert-butyl group of one molecule in the asymmetric unit of the β-form rotated by ca. 60 • , and the dihedral angle between the phenyl and salicyl planes increased slightly in the β-form crystal. However, the changes in the molecular conformation and packing arrangement are small, which leads to the reversible SCSC phase transition with no destruction of the crystal lattice. The dielectric constant along the b-axis was small, probably due to the weak intermolecular interactions in the crystals.

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“…29 This has been attributed to first order displacive solid-solid transition that occurs with Bain distortion. [38][39][40][41] Elastic properties in molecular solids are largely determined by the isotropy of crystal packing. 8,18 Recent studies by Ghosh and Reddy on caffeine co-crystals have established that bending of elastic organic crystals is related to isotropic packing with the presence of relatively weak and dispersive interactions in all directions.…”

Section: Introductionmentioning

confidence: 99%

Dual Stress and Thermally Driven Mechanical Properties of the Same Organic Crystal: 2,6-Dichlorobenzylidene-4-fluoro-3-nitroaniline

et al. 2015

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An elastic organic crystal, 2,6-dichlorobenzylidine-4-fluoro-3-nitroaniline (DFNA), which also shows thermosalient behavior, is studied. The presence of these two distinct properties in the same crystal is unusual and unprecedented because they follow respectively from isotropy and anisotropy in the crystal packing. Therefore, while both properties lead from the crystal structure, the mechanisms for bending and thermosalience are quite independent of one another. Crystals of the low-temperature (α) form of the title compound are bent easily without any signs of fracture with the application of deforming stress, and this bending is within the elastic limit. The crystal structure of the α-form was determined (P21/c, Z = 4, a = 3.927(7) Å, b = 21.98(4) Å, c = 15.32(3) Å). There is an irreversible phase transition at 138 °C of this form to the high-temperature β-form followed by melting at 140 °C. Variable-temperature X-ray powder diffraction was used to investigate the structural changes across the phase transition and, along with an FTIR study, establishes the structure of the β-form. A possible rationale for strain build-up is given. Thermosalient behavior arises from anisotropic changes in the three unit cell parameters across the phase transition, notably an increase in the b axis parameter from 21.98 to 22.30 Å. A rationale is provided for the existence of both elasticity and thermosalience in the same crystal. FTIR studies across the phase transition reveal important mechanistic insights: (i) increased π···π repulsions along [100] lead to expansion along the a axis; (ii) change in alignment of C-Cl and NO2 groups result from density changes; and (iii) competition between short-range repulsive (π···π) interactions and long-range attractive dipolar interactions (C-Cl and NO2) could lie at the origin of the existence of two distinctive properties.

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A series of compounds forming polar crystals and showing single-crystal-to-single-crystal transitions between polar phases

Cited by 48 publications

References 46 publications

Contemporary Diffraction Methods in Study of Polycrystals

Contemporary Diffraction Methods in Study of Polycrystals

Reversible Single-Crystal-to-Single-Crystal Phase Transition of Chiral Salicylidenephenylethylamine

Dual Stress and Thermally Driven Mechanical Properties of the Same Organic Crystal: 2,6-Dichlorobenzylidene-4-fluoro-3-nitroaniline

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