Isolated versus Condensed Anion Structure II; the Influence of the Cations (1,3-propanediammonium, 1,4-phenylendiammonium, and n-propylammonium) on Structures and Phase Transitions of CdBr2-4Salts A 79,81Br NQR and X-ray Structure Analysis

1996 ◽  
Vol 51 (12) ◽  
pp. 1216-1228 ◽  
Author(s):  
Hideta Ishihara ◽  
Shi-qi Dou ◽  
Keizo Horiuchi ◽  
V. G. Krishnan ◽  
Helmut Paulus ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Phase I ◽  
Chain Structure ◽  
Phase Iii ◽  
X Ray ◽  
Dsc Measurements ◽  
Structure Determinations ◽  
A Chain ◽  
Successive Phase ◽  
Phase Iv

Abstract The influence of the cations on the condensation of anions CdBr42- in salts (A')CdBr4 (II) and (A)2CdBr4 (II) is studied by 79,81Br NQR and X-ray crystal structure determinations. (A')CdBr4 : A' = [H3N(CH2)3NH3]2+ (1) crystallizes with a layer-type anion structure at 298 K and A' = [1,4-(H3N)2C6H4]2+ (2) crystallizes with a chain-type anion structure at 298 K. (A)2 CdBr4 : A = [n-H3C(CH2)2NH3]+ (3) crystallizes with a layer-type anion structure at 293 K. (1) shows successive phase transitions at 328, 363, and 495 K according to the NQR and DSC measurements. Phase IV of (1): at 298 K orthorhombic, Pnma, Z = 4,a = 772.1 (4), b = 1905.4(9), c = 789.8(4) pm. 81Br NQR spectrum showed a doublet at 77 K (phase IV) with ν1= 61.177 and ν2 = 45.934 MHz and also a doublet at 350 K (phase III) with ν1= 57.581 and ν2 = 48.747 MHz. (2): at 295 K orthorhombic, Pnma, Z = 4, a = 802.5(3), b = 1775.1(6), c = 881.9(3) pm; the five-coordinated Cd atom and one-dimensional [CdBr4]2- anion chain structure was observed. This coordination and chain structure are very rare for (A')CdX4 (II) or (A)2CdX4 (II). Two 81Br NQR lines were observed at 77 K: ν1= 70.159 and ν3 = 40.056 MHz. One more line appeared at 85 K: ν2 = 53.622 MHz. A 81Br NQR triplet was observed at 273 K: ν1 = 67.919, ν2 = 56.317, and ν3 = 40.907 MHz. (3) shows successive phase transitions at 121, 135, 165, and 208 K according to the NQR, DSC, and DTA measurements. Phase I of (3): at 293 K orthorhombic, Cmca, Z = 4, a = 783.4(4), b = 2480.2(10), c = 806.5(4) pm. 81Br NQR doublet was observed at 77 K (phase V) and at 300 K (Phase I) with ν1 = 61.060 and ν2 = 54.098 MHz (77 K); v1 = 55.835 and ν2 = 55.964 MHz (373 K). No NQR line could be observed in phases II, III, and IV.

X-ray studies of the phase transitions of bis(guanidinium)zirconium bis(nitrilotriacetate) hydrate, (C(NH2)3)2Zr(N(CH2COO)3)2 · H2O

1999 ◽  
Vol 214 (3) ◽  
Author(s):  
J. Schreuer ◽  
E. Haussühl
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Phase I ◽  
Phase Iii ◽  
Group Symmetry ◽  
Translational Symmetry ◽  
X Ray Diffraction ◽  
Space Group Symmetry ◽  
X Ray ◽  
Structural Differences

AbstractThe structural differences of phase I (at 193 K) and phase III (293 K) of bis(guanidinium)zirconium bis(nitrilotriacetate) hydrate were investigated by means of X-ray diffraction. The phase transition III → I is characterised by a loss of translational symmetry as it is indicated by the change of space group symmetry from

Syntheses, Structural Characterization and Fluorescence of Zn(II) and Cd(II) Polymers from 5-(Pyridin-2-ylmethylamino)isophthalic acid

2013 ◽  
Vol 68 (9) ◽  
pp. 1007-1014 ◽  
Author(s):  
Xiao-Chun Cheng ◽  
Xiao-Hong Zhu ◽  
Hai-Wei Kuai
Keyword(s):  
Water Clusters ◽  
Hydrothermal Reaction ◽  
Reaction System ◽  
Chain Structure ◽  
Isophthalic Acid ◽  
Auxiliary Ligand ◽  
X Ray Diffraction ◽  
X Ray ◽  
Alkaline Reaction ◽  
A Chain

The hydrothermal reaction of Zn(II) nitrate with 5-(pyridin-2-ylmethylamino)isophthalic acid (H2L) yields the complex [Zn(L)(H2O)] 2H2O (1). When 2,2'-bipyridine (bpy) as auxiliary ligand and Cd(II) nitrate were used in the alkaline reaction system, [Cd(L)(H2O)(bpy)] 3H2O (2) was obtained. Complexes 1 and 2 have been characterized by single-crystal and powder X-ray diffraction, IR, elemental and thermogravimetric analyses. Complex 1 shows a 2D fes network structure with uninodal 3-connected (4.82) topology, which is further linked by hydrogen bonding to give rise to a 3D supramolecular framework; complex 2 displays a chain structure. Interestingly, tetranuclear water clusters were generated in 1, which are interlinked to fabricate a water chain structure. The fluorescence properties of 1 and 2 were investigated

scholarly journals Etude par resonance magnetique des mouvements moléculaires dans l'acrylonitrile solide

1973 ◽  
Vol 51 (23) ◽  
pp. 3889-3900 ◽  
Author(s):  
Buu Ban ◽  
C. CHACHATY
Keyword(s):  
Phase Transitions ◽  
Phase I ◽  
Phase Ii ◽  
Phase Iii ◽  
Solid Matrix ◽  
Peroxy Radicals ◽  
Γ Irradiation ◽  
Rotational Oscillation ◽  
Résonance Magnétique ◽  
Oxygen Addition

Phase transitions and molecular motions in solid acrylonitrile and its deuterated homologue CH2=CDCN, have been studied between 100 and 191 °K (m.p.) by wide line n.m.r. and by T1 relaxation time measurements. Phase I (164 °K < T < 191 °K) is trapped and becomes metastable by quick cooling of acrylonitrile at 77 °K. It changes into the phase II, stable between 113 °K and 164 °K by a long duration annealing at 155–160 °K. The phase II → phase III transition occurs at 113 °K. It may be assumed that phase III, stable below this temperature, is rigid at T < 105 °K. Phase II may be characterized by a rotational oscillation of molecules around an axis defined by the N atom and the middle of the vinyl double bond. In phase I, acrylonitrile molecules undergo a binary reorientation motion around this axis with an activation energy of 4.2 kcal mol−1. The motion of peroxy radicals, trapped in acrylonitrile has been also studied by e.s.r. These radicals were produced by oxygen addition to free radicals previously formed by γ irradiation of acrylonitrile at 77 °K. The g anisotropy variation with temperature, shows no discontinuities at phase transitions, the activation of reorientation of peroxy radicals being 0.65 kcal mol−1. This result suggests that we are dealing in fact with macroradicals, the internal rotation of which is only observable in a solid matrix.

Vibrational spectra of crystalline malononitrile

1976 ◽  
Vol 54 (20) ◽  
pp. 3293-3302 ◽  
Author(s):  
R. Savoie ◽  
R. Brousseau ◽  
C. Nolin
Keyword(s):  
Phase I ◽  
Metastable Phase ◽  
Phase Iii ◽  
Site Symmetry ◽  
Monoclinic System ◽  
X Ray ◽  
Data Phase ◽  
Quadrupole Resonance ◽  
Resonance Data ◽  
Nuclear Quadrupole

The infrared and Raman spectra of the four solid phases of malononitrile have been recorded. The crystal structures of these solids are now relatively well established from the present results and from previous X-ray and nuclear quadrupole resonance data. Phase I belongs to the P21/n space group of the monoclinic system, with four molecules per unit cell. In phase II, the molecules occupy two sets of general positions in a crystal of P21 symmetry. The molecular site symmetry is Cs in phase III which is highly symmetric. The structure of the low-temperature metastable phase IV appears to be very similar to that of phase I.

Preparation and Structural Characterization of Chain Ni (II) Coordination Polymer Material

2011 ◽  
Vol 322 ◽  
pp. 369-372
Author(s):  
Zhi Xiang Ji
Keyword(s):  
Coordination Polymer ◽  
Polymer Material ◽  
Chain Structure ◽  
Monoclinic Space Group ◽  
Dimensional Chain ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
X Ray ◽  
A Chain

A chain Ni (II) coordination polymer material was prepared and characterized by elemental analysis and single-crystal X-ray diffraction. It crystallizes in monoclinic, space group C2/c with a = 1.24348(13) nm, b = 1.29477(12) nm, c = 1.51480(17) nm and Dc = 1.401 g•cm-3. The results of structural analysis indicated that each Ni (II) ion forms six-coordinated with nitrogen atoms of pyridine and thiocyanate, and the Ni (II) coordination polymer material formed one dimensional chain structure by the interaction of pyridine rings.

Darstellung und Kristallstruktur von K2Pd02 / Synthesis and Crystal Structure of K2Pd02

1974 ◽  
Vol 29 (1-2) ◽  
pp. 10-12 ◽  
Author(s):  
Horst Sabrowsky ◽  
Welf Bronger ◽  
Dieter Schmitz
Keyword(s):  
Crystal Structure ◽  
Structure Type ◽  
Chain Structure ◽  
Unit Cell ◽  
One Dimension ◽  
Ternary Oxide ◽  
Orthorhombic Unit Cell ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
A Chain

The ternary oxide K2PdO2 has been prepared by a reaction between K2O and PdO. X-ray investigations suggest a chain-structure-type which corresponds to that of K2PtS2. The planar oxygen coordinations of the palladium atoms are connected laterally in one dimension. The orthorhombic unit cell (a = 8.523, b = 6.089, c = 3.119 Å) contains two formula units.

Phase transitions and ferroelectricity in NaSb3F10

2008 ◽  
Vol 42 (1) ◽  
pp. 58-62 ◽  
Author(s):  
R. J. Christie ◽  
P. K. Wu ◽  
P. Photinos ◽  
S. C. Abrahams
Keyword(s):  
Phase Transitions ◽  
Phase I ◽  
Thermal Hysteresis ◽  
Entropy Change ◽  
Pyroelectric Coefficient ◽  
Phase Iii ◽  
Space Group ◽  
Heating And Cooling ◽  
Order Of Magnitude ◽  
First Order Phase

Atomic coordinate analysis allows materials with appropriate but previously unrecognized dielectric properties to be predicted as new ferroelectrics if their crystal structure is known. An earlier such prediction that NaSb3F10is ferroelectric is confirmed herein without ambiguity. Its spontaneous polarizationPsis found to exhibit reproducible dielectric hysteresis at room temperature, withPs≃ 60 µC m−2, under the application of a field of 0.3 MV m−1or greater. The pyroelectric coefficient 〈p〉 = 17 (5) µC m−2 K−1at 298 K. NaSb3F10undergoes a phase transition atTC≃ 461 K, on correction for thermal hysteresis, with entropy change ΔS= 5.7 (3) J mol−1 K−1. The colorless crystals melt atTm ≃ 515 K and decompose above ∼600 K. The thermal hysteresis of ∼35 K inTC, on heating and cooling at 5–25 K min−1, is typical of first-order phase transitions. The space group in ferroelectric phase III isP63, and that in phase II is predicted to beP6322, a nonpolar supergroup ofP63; the supergroup expected in the prototypic nonferroic phase I isP63/mmc. The space group of phase III isnota direct subgroup of phase I. The dielectric permittivity ∊′ at 1 kHz increases over an order of magnitude between 300 K and a major inflection atTC, continuing to increase steadily thereafter toTm.

Structures and phase transitions in a new ferroelectric – pyridinium chlorochromate – studied by X-ray diffraction, DSC and dielectric methods

2012 ◽  
Vol 68 (2) ◽  
pp. 128-136 ◽  
Author(s):  
Hanna Małuszyńska ◽  
Piotr Czarnecki ◽  
Anna Czarnecka ◽  
Zdzisław Pająk
Keyword(s):  
Phase Transitions ◽  
Pyridinium Salt ◽  
Diffraction Method ◽  
Phase Iii ◽  
Pyridinium Chlorochromate ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Intermediate Phases ◽  
Ferroelectric Hysteresis

Pyridinium chlorochromate, [C5H5NH]+[ClCrO3]− (hereafter referred to as PyClCrO3), was studied by X-ray diffraction, differential scanning calorimetry (DSC) and dielectric methods. Studies reveal three reversible phase transitions at 346, 316 and 170 K with the following phase sequence: R\bar 3m (I) → R3m (II) → Cm (III) → Cc (IV), c′ = 2c. PyClCrO3 is the first pyridinium salt in which all four phases have been successfully characterized by a single-crystal X-ray diffraction method. Structural results together with dielectric and calorimetric studies allow the classification of the two intermediate phases (II) and (III) as ferroelectric with the Curie point at 346 K, and the lowest phase (IV) as most probably ferroelectric. The ferroelectric hysteresis loop was observed only in phase (III). The high ionic conductivity hindered its observation in phase (II).

From six- to five-coordinated SbIII in [(CH3)3PH]3[Sb2Cl9]: transition pathways from single-crystal X-ray diffraction

2008 ◽  
Vol 64 (5) ◽  
pp. 558-566 ◽  
Author(s):  
Anna Gagor ◽  
Maciej Wojtaś ◽  
Adam Pietraszko ◽  
Ryszard Jakubas
Keyword(s):  
Phase Transitions ◽  
Phase I ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Octahedral Environment ◽  
Transition Pathways ◽  
Cl Atoms ◽  
Unusual Increase

[(CH3)3PH]3[Sb2Cl9] experiences four phase transitions which were found by means of calorimetry, thermogravimetry and X-ray diffraction. The crystal structure was solved in the space group P63/mmc at 382 K (phase I), Pnam at 295 K (phase II) and Pna21 at 175 K (phase V). We observed an unusual increase in symmetry from the monoclinic to the orthorhombic form at the IV\rightarrowV transition. The parent hexagonal high-temperature phase I consists of highly disordered [(CH3)3PH]+ cations and [Sb2Cl9]3− anions with an octahedral environment of SbIII. The transition from phases I to II is associated with the ordering of [(CH3)3PH]+ cations. Moreover, the successive transformations from phases I to V are related to the change in the arrangement of Cl atoms in [Sb2Cl9]3− anions from the discrete `face-sharing bioctahedra' (phase I) to two corner-sharing square pyramids. A mechanism for the phase transitions is proposed. It is observed that weak C—H...Cl interactions are responsible for the structure arrangement in low-temperature phases.

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