X-ray single crystal analysis of the phase transitions in NH4MnCl3. Some Mossbauer-X-ray spectra relations

The organic–inorganic hybrid compound 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2] (4apFeS), was obtained by slow evaporation of the solvent at room temperature and characterized by single-crystal X-ray diffraction in the temperature range from 290 to 80 K. Differential scanning calorimetry revealed that the title compound undergoes a sequence of three reversible phase transitions, which has been verified by variable-temperature X-ray diffraction analysis during cooling–heating cycles over the temperature ranges 290–100–290 K. In the room-temperature phase (I), space group C2/c, oxygen atoms from the closest Fe-atom environment (octahedral) were disordered over two equivalent positions around a twofold axis. Two intermediate phases (II), (III) were solved and refined as incommensurately modulated structures, employing the superspace formalism applied to single-crystal X-ray diffraction data. Both structures can be described in the (3+1)-dimensional monoclinic X2/c(α,0,γ)0s superspace group (where X is ½, ½, 0, ½) with modulation wavevectors q = (0.2943, 0, 0.5640) and q = (0.3366, 0, 0.5544) for phases (II) and (III), respectively. The completely ordered low-temperature phase (IV) was refined with the twinning model in the triclinic P{\overline 1} space group, revealing the existence of two domains. The dynamics of the disordered anionic substructure in the 4apFeS crystal seems to play an essential role in the phase transition mechanisms. The discrete organic moieties were found to be fully ordered even at room temperature.

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Raman and single-crystal X-ray diffraction evidence of pressure-induced phase transitions in a perovskite-like framework of [(C3H7)4N] [Mn(N(CN)2)3]

Dalton Transactions ◽

10.1039/c9dt01648a ◽

2019 ◽

Vol 48 (25) ◽

pp. 9072-9078 ◽

Cited By ~ 9

Author(s):

Mirosław Mączka ◽

Ines E. Collings ◽

Fabio Furtado Leite ◽

Waldeci Paraguassu

Keyword(s):

Phase Transitions ◽

Single Crystal ◽

X Ray Diffraction ◽

X Ray ◽

Lower Symmetry

The [TPrA][Mn(dca)3] perovskite shows highly anisotropic compression and the presence of three pressure-induced phase transitions near 0.4, 3 and 5 GPa into lower symmetry phases.

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The modulated structure of the calcium aluminate Ca6(AlO2)12·Bi2O3

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768110035792 ◽

2010 ◽

Vol 66 (6) ◽

pp. 585-593 ◽

Cited By ~ 2

Author(s):

O. Pérez ◽

S. Malo ◽

M. Hervieu

Keyword(s):

Single Crystal ◽

Calcium Aluminate ◽

Three Dimensional ◽

X Ray Diffraction ◽

Electron Pairs ◽

Modulated Structure ◽

X Ray ◽

Trigonal Bipyramidal ◽

Superspace Formalism ◽

Single Crystal Analysis

Bismuth calcium aluminate, Bi2Ca6Al12O27, has been prepared as a ceramic and a single crystal. Analysis of reciprocal space using both electron and X-ray diffraction show an R-centred hexagonal unit cell: a = b = 17.3892 (4), c = 6.986 (1) Å. Additional weak reflections are observed; they require the introduction of a modulation wavevector q = 0.0453 (2)c* for indexing. The modulated structure has been solved using the superspace formalism [superspace group X\overline{3}(00\gamma)0]. A framework of corner-sharing AlO4 tetrahedra forms corrugated sixfold rings and uncommon triple rings. The Ca2+ cations exhibit an eightfold coordination sphere; edge-sharing CaO8 polyhedra form intertwinned zigzagging rows along c creating a three-dimensional net. Bi atoms are located in large hexagonal tunnels parallel to c and form Bi2O3 pairs, which adopt a trigonal bipyramidal configuration. The 6s 2 lone-electron pairs (Lp) point along c, in the opposite direction to the three Bi—O strong bonds to form two BiO3Lp tetrahedra with a common base. Different orientations of the Bi2O3Lp2 pairs, rotated by 60° around c, are observed. Their stacking modes in each of the hexagonal tunnels are described. The sequence of the stacking varies along c in each of the tunnels.

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Structural Phase Transitions of Endohedral Metallofullerene La@C82 Studied by Single Crystal X-Ray Diffraction

Molecular Crystals and Liquid Crystals Science and Technology Section A Molecular Crystals and Liquid Crystals ◽

10.1080/10587250008025539 ◽

2000 ◽

Vol 340 (1) ◽

pp. 639-642 ◽

Cited By ~ 12

Author(s):

Tetsu Watanuki ◽

Akihiko Fujiwara ◽

Kenji Ishii ◽

Yasuyuki Matuoka ◽

Hiroyoshi Suematsu ◽

...

Keyword(s):

Phase Transitions ◽

Single Crystal ◽

Structural Phase ◽

Structural Phase Transitions ◽

X Ray Diffraction ◽

X Ray ◽

Endohedral Metallofullerene

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Reversiblechair↔skewconformational interconversion of 1,3,2-dioxaphosphorinane ring in the solid state

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520615020259 ◽

2016 ◽

Vol 72 (1) ◽

pp. 117-125 ◽

Cited By ~ 2

Author(s):

Katarzyna Anna Ślepokura

Keyword(s):

Phase Transitions ◽

Single Crystal ◽

Dihydroxyacetone Phosphate ◽

Temperature Phase ◽

Coordination Geometry ◽

Phosphate Anion ◽

X Ray ◽

X Ray Crystallography ◽

Cyclic Phosphate ◽

Low Temperature Phase

β-NH4[(MeO)2cDHAP] (where cDHAP is cyclic dihydroxyacetone phosphate) has been investigated by X-ray crystallography in the temperature range 350–100 K. Three reversible single-crystal-to-single-crystal phase transitions have been examined and four phases (high-, room-, medium- and low-temperature phase, HTP, RTP, MTP and LTP, respectively) have been structurally determined: HTP (at 350 K,P21/a,Z= 24), RTP (290 K, P \overline{1},Z= 12), MTP (205 K,P21/a,Z= 4) and LTP (100 K, P \overline{1},Z= 24). Various puckering modes of the 1,3,2-dioxaphosphorinane ring of the organic cyclic phosphate anion have been revealed in the crystal:chairandskew. Thechair↔skewring flipping, which has been shown to take place during the phase transitions, results in various populations ofskewandchairconformers in different phases. The flexibility in the coordination geometry of ammonium cations is considered to assist in the conformational flexibility of the dioxaphosphorinane ring.

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