Phase Diagram of the Orientationally Order-disorder Binary System 2,2-dimethyl-1,3-propanediol / 2,2-dimethyl-1,3-diaminopropane, [(CH3)2 C(CH2OH)2]x [(CH3)2C(CH2NH2)2]1-x · A Thermodynamic, X-ray, and 1H-NMR study

1996 ◽  
Vol 51 (7) ◽  
pp. 871-881 ◽  
Author(s):  
Roman Strauss ◽  
Sigmar Braun ◽  
Shi-qi Dou ◽  
Hartmut Fuess ◽  
Alarich Weiss
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Binary System ◽  
Phase I ◽  
1H Nmr ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
H Nmr

AbstractThe phase diagram of the binary system [2,2-dimethyl-1,3-propanediol]x (1) / [2,2-dimethyl-1,3- diaminopropane]1-x (2) was studied by X-ray diffraction and DTA/DSC, for (2) also by 1H-NMR. The system is miscible over the whole concentration range 0 ≤ x ≤ 1 in the liquid state and in the plastic solid state, phase I, just below the melting point. At lower temperatures the system is demixing, and at room temperature two plastic mixed crystals coexist. The plastic phases of (1), (2), and (l)x(2)1-x crystallize face centered cubic, Fm3m, Z = 4, the lattice constants decreasing linearely with increasing x, and the lattice constants are: (1) a(327K) = 880.3 pm , (2) a(243K) = 905.6 pm. By single crystal X-ray diffraction the structure of the ordered phase II of (1) was refined at room temperature, monoclinic, P21/n, Z = 4, a = 596.9 pm, b = 1090.2 pm, c = 1011.0 pm, β = 99.74°. The results are in good agreement with the literature. The phase transition temperatures (in Kelvin) are T1→m = 399.2, TMm→1 = 399.7, T11→1 = 316.2, T1→11 = 308.2 for (1); = 300.2, = 301.7, T11→1 = 228.7, T1→n = 194.2 for (2). Strong hysteresis is observed for the transition T1→11 in (2). In the mixed systems (1)x(2)1-x, 0 < x < 1, the disordered phases do not order even by quenching to liquid nitrogen temperature. High resolution 1 H-NMR measurements are reported for phase I of (2) as a function of temperature. The “liquid” 1H-NMR spectrum is present far below the thermodynamic phase transition temperature T11-1, overlapping the wide line unresolved powder spectrum of phase II.

1H NMR study of the solvolysis of the paramagnetic tetrachloro-bis(imidazole)ruthenium(III) anion in water, methanol, and dimethyl sulfoxide

1995 ◽  
Vol 73 (4) ◽  
pp. 471-482 ◽  
Author(s):  
Craig Anderson ◽  
André L. Beauchamp
Keyword(s):  
Dimethyl Sulfoxide ◽  
1H Nmr ◽  
Room Temperature ◽  
Single Species ◽  
X Ray Diffraction ◽  
Chloro Complexes ◽  
X Ray ◽  
H Nmr ◽  
Nmr Study ◽  
Nmr Signals

The 1H NMR signals of the Ru(III) species present in solution are considerably broadened and shifted by paramagnetism, but they can be used to follow chloride displacement in the trans-[RuCl4Im2]− ion. This anion remains predominant for several hours at room temperature in D2O, but its signals are progressively replaced by those of a monoaqua [RuCl3(D2O)Im2] complex. Over a period of days, two new sets of peaks appear, corresponding to two isomers of [RuCl2(D2O)2Im2]+. The same behaviour is observed for the 1-methyl-and 4-methylimidazole analogues. These reactions can be driven backwards by addition of KCl, but [RuCl4Im2]− is not quantitatively regenerated in solution even for 6 M NaCl. Within several months, the [RuCl2(D2O)2Im2]+ isomers further aquate to a single species [RuCl(D2O)3Im2]2+. In CD3OD, displacement of the first chloride of [RuCl4Im2]− takes place faster, over several hours, but substitution stops at the [RuCl3(CD3OD)Im2] stage. In DMSO, substitution occurs very slowly. The [RuCl3(DMSO)Im2]:[RuCl4Im2]−mixture (1:2) obtained after 12 days starts to show very slow reduction to two Ru(II) species, one of which precipitates as yellow crystals. From X-ray diffraction work (monoclinic, P21/n, a = 9.951, b = 8.564, c = 10.527 Å, β = 92.95°, R = 0.033), the compound was identified as [RuCl2(DMSO-d6)2Im2], where the metal has a trans-trans-trans coordination and the DMSO ligands are S-bonded. Keywords: paramagnetic ruthenium anion, solvolysis, chloro complexes.

scholarly journals Studies of Structure and Phase Transition in [C(NH2)3]HgBr3 and [C(NH2)3]HgI3 by Means of Halogen NQR, 1H NMR, and Single Crystal X-Ray Diffraction

2000 ◽  
Vol 55 (1-2) ◽  
pp. 230-236 ◽  
Author(s):  
Hiromitsu Terao ◽  
Masao Hashimoto ◽  
Shinichi Hashimoto ◽  
Yoshihiro Furukawa
Keyword(s):  
Phase Transition ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Order ◽  
H Nmr ◽  
Trigonal Bipyramidal ◽  
Second Order Phase Transition

(TThe crystal structure of [C(NH2)3]HgBr3 was determined at room temperature: monoclinic, space group C2/c, Z = 4, a = 775.0(2), b = 1564.6(2), c = 772.7(2) pm, β = 109.12(2)°. In the crystal, almost planar HgBr3- ions are connected via Hg ··· Br bonds, resulting in single chains of trigonal bipyramidal HgBr5 units which run along the c direction. [C(NH2)3]HgI3 was found to be isomorphous with the bromide at room temperature. The temperature dependence of the halogen NQR frequencies (77 < 77K < ca. 380) and the DTA measurements evidenced no phase transition for the bromide, but a second-order phase transition at (251 ± 1) K (Tc1) and a first-order one at (210 ± 1) K for the iodide. The transitions at Tc2are accompanied with strong supercooling and significant superheating. The room temperature phase (RTP) and the intermediate temperature phase (ITP) of the iodide are characterized by two 127I(m=1/2↔3/2) NQR lines which are assigned to the terminal and the bridging I atoms, respectively. There exist three lines in the lowest temperature phase (LTP), indicating that the resonance line of the bridging atom splits into two. The signal intensities of the 127I(m =1/2↔3/2) NQR lines in the LTP decrease with decreasing temperature resulting in no detection below ca. 100 K. The 127I(m=1/2↔3/2) NQR frequency vs. temperature curves are continuous at Tcl, but they are unusual in the LTP. The T1vs. Tcurves of 1H NMR for the bromide and iodide are explainable by the reorientational motions of the cations about their pseudo three-fold axes. The estimated activation energies of the motions are 35.0 kJ/mol for the bromide, and 24.1, 30.1, and 23.0 kJ/mol for the RTP, FTP, and LTP of the iodide, respectively

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

Rotational Polymorphism of Methyl-Substituted Ammonium Perchlorates

1965 ◽  
Vol 9 ◽  
pp. 170-189 ◽  
Author(s):  
M. Stammler ◽  
R. Bruenner ◽  
W. Schmidt ◽  
D. Orcutt
Keyword(s):  
Phase Transition ◽  
Ammonium Perchlorate ◽  
Room Temperature ◽  
Decomposition Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Techniques ◽  
Cell Dimensions ◽  
Thermal Analysis Techniques ◽  
Space Requirements

AbstractThe thermal transformations which take place in solid methyl-substituted ammonium perchlorates have been studied using high-temperature X-ray diffraction and differential thermal analysis techniques. In the temperature range from 20°C to their decomposition temperature (above 300°C), ammonium perchlorate and tetramethyl ammonium perchlorate undergo only one enantiomorphic phase transition, namely at 240 and 340°C (with decomposition), respectively. This I—II transition is ascribed to the beginning of the free rotation of the ClO4− ions. The rotation of the cations, however, begins below room temperature. If the symmetry of the cation is lowered by having both methyl groups and hydrogens arranged around the nitrogen (as in monomethyl, dimethyl, and trimethyl ammonium perchlorates), there is an additional enantiomorphic phase transition. This I—II transformation is ascribed to the rotation of the cations which have, in the partially substituted ions, two sets of non-equivalent symmetry axes (different moments of inertia). The temperatures of transformation are discussed in terms of the space requirements for rotation. Symmetries and cell dimensions of some modifications were determined.

Structure and phase transition of the Se-rich variety of antimonpearceite, [(Ag,Cu)6(Sb,As)2(S,Se)7][Ag9Cu(S,Se)2Se2]

2006 ◽  
Vol 62 (5) ◽  
pp. 768-774 ◽  
Author(s):  
Michel Evain ◽  
Luca Bindi ◽  
Silvio Menchetti
Keyword(s):  
Phase Transition ◽  
Room Temperature ◽  
Atomic Displacement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dimensional Diffusion ◽  
Ionic Conducting ◽  
Local Arrangement ◽  
Diffusion Paths ◽  
Linear Coordination

The crystal structure of a Se-rich antimonpearceite has been solved and refined by means of X-ray diffraction data collected at temperatures above (room temperature) and below (120 K) an ionic conductivity-induced phase transition. Both structure arrangements consist of the stacking of [(Ag,Cu)6(Sb,As)2(S,Se)7]2− A (A′) and [Ag9Cu(S,Se)2Se2]2+ B (B′) module layers in which Sb forms isolated SbS3 pyramids typically occurring in sulfosalts; copper links two S atoms in a linear coordination, and silver occupies sites with coordination ranging from quasi-linear to almost tetrahedral. In the ionic-conducting form, at room temperature, the silver d 10 ions are found in the B (B′) module layer along two-dimensional diffusion paths and their electron densities described by means of a combination of a Gram–Charlier development of the atomic displacement factors and a split-atom model. The structure resembles that of pearceite, except for the presence of both specific (Se) and mixed (S, Se) sites. In the low-temperature `ordered' phase at 120 K the silver d 10 ions of the B (B′) module layer are located in well defined sites with mixed S—Se coordination ranging from quasi-linear to almost tetrahedral. The structure is then similar to that of 222-pearceite but with major differences, specifically its cell metric, symmetry and local arrangement in the B (B′) module layer.

Phase Transition of C5H5 NHSbBr4 Having a Hypervalent Bond: A 2H NMR and X-Ray Diffraction Study [Phase Transition of C5H5NHSbBr4]

1996 ◽  
Vol 51 (5-6) ◽  
pp. 739-744
Author(s):  
K. Yamada ◽  
T. Ohtani ◽  
S. Shirakawa ◽  
H. Ohki ◽  
T. Okuda ◽  
...  
Keyword(s):  
Phase Transition ◽  
Nearest Neighbor ◽  
Study Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Deuterated Analog ◽  
Librational Motion ◽  
Diffraction Patterns

Abstract The second order phase transition at 253 K of pyridinium tetrabromoantimonate(III), C5H5NHSbBr4 , has been characterized by means of X-ray diffraction and 2H NMR. As was suggested from the 81Br NQR spectra, the Rietveld refinements of the X-ray diffraction patterns at 297 K and 116 K confirm the structural change of the anion from SbBr-4 to SbBr3 • Br-. The line shape analysis of the 2H NMR using the deuterated analog revealed that the librational amplitude of the pyridinium ring about the axis normal to the plane increased with temperature and its rms amplitude reaching ca. 25° at Tc . The librational motion may induce the phase transition breaking the hydrogen bonds of the type N-H … Br. However, nearest-neighbor 2π/6 jump or reorientation such as seen in benzene were not observed even at 350 K.

STUDY ON PHASE DIAGRAM OF BaO-Y2O3-CuO TERNARY SYSTEM

1987 ◽  
Vol 01 (02) ◽  
pp. 363-365 ◽  
Author(s):  
Guangcan Che ◽  
Jingkui Liang ◽  
Wei Chen ◽  
Sishen Xie ◽  
Yude Yu ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Phase Diagram ◽  
Ternary System ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
High Tc Superconductor

In Ba-R-Cu-O system (R=La, Y) , high Tc superconductor have been discovered (1–3). The room temperature section of the phase diagram in BaO-Y2O3-CuO system has been completed by means of X-ray diffraction, thermal analysis and superconducting measurements.

scholarly journals Lactide polymerization with iron alkoxide complexes

2015 ◽  
Vol 93 (6) ◽  
pp. 594-601 ◽  
Author(s):  
Arek Keuchguerian ◽  
Berline Mougang-Soume ◽  
Frank Schaper ◽  
Davit Zargarian
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Side Reactions ◽  
X Ray Diffraction ◽  
Iron Cluster ◽  
X Ray ◽  
H Nmr ◽  
Exchange Product

This report presents the results of a study on the preparation of iron alkoxide complexes chelated by diiminopyridine ligands and their role in the room temperature polymerization of rac-lactide. Reaction of N,N′-(p-R-C6H4CH2)2-diiminopyridines (R = H (1), F (2)) with FeX2 (X = Cl, Br) yielded the homoleptic complexes [(1)2Fe][FeX4] or [(2)2Fe][FeX4], respectively. Treating the latter with Na[BPh4] afforded the anion exchange product [(2)2Fe][BPh4]2, which was characterized by 1H NMR and absorption spectroscopy, combustion analysis, and single crystal X-ray diffraction. Various attempts to grow crystals of [(1)2Fe][FeX4] and [(2)2Fe][FeX4] culminated in the isolation of single crystals of [(2)2Fe][Cl6Fe2O] that was characterized by X-ray diffraction. Attempted synthesis of well-defined, mononuclear alkoxide derivatives from [(1)2Fe]2+ or [(2)2Fe]2+ gave mostly intractable products, but in one case we obtained the crystallographically characterized sodium iron cluster Na4Fe2(OC6H4F)8(THF)2. An aryloxide derivative proved accessible by reaction of NaOC6H4F with the mono-ligand precursor LFeCl2 (L = N,N′-dimesityl-diiminopyridine), but characterization of LFe(OC6H4F)2 was limited to a single crystal X-ray diffraction analysis, owing to unsuccessful attempts at isolating pure samples. The difficulties encountered in the isolation of pure alkoxide derivatives prompted us to use in-situ generated LFe(OEt)2 for studying the polymerization of rac-lactide. This system was found to be moderately active at room temperature and with a slight preference for the formation of a heterotactic polymer (Pr = 0.54–0.65). Large polydispersities of 1.5–2.0 indicated the presence of transesterification side-reactions, which were confirmed by the presence of peaks with m/z = n 144 + M(EtOH) + M(Na+) and m/z = (n + 0.5) 144 + M(EtOH) + M(Na+) in MALDI-MS.

scholarly journals Structural Study of δ-AlOOH Up to 29 GPa

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1055
Author(s):  
Dariia Simonova ◽  
Elena Bykova ◽  
Maxim Bykov ◽  
Takaaki Kawazoe ◽  
Arkadiy Simonov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Synchrotron Radiation ◽  
Equation Of State ◽  
Room Temperature ◽  
Diamond Anvil Cell ◽  
Volume Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diamond Anvil ◽  
Murnaghan Equation

A structure and equation of the state of δ-AlOOH has been studied at room temperature, up to 29.35 GPa, by means of single crystal X-ray diffraction in a diamond anvil cell using synchrotron radiation. Above ~10 GPa, we observed a phase transition with symmetry changes from P21nm to Pnnm. Pressure-volume data were fitted with the second order Birch-Murnaghan equation of state and showed that, at the phase transition, the bulk modulus (K0) of the calculated wrt 0 pressure increases from 142(5) to 216(5) GPa.

Phase Diagram and Cation Dynamics of Mixed MA1-xFAxPbBr3 Hybrid Perovskites

2021 ◽  
Author(s):  
Mantas Simenas ◽  
Sergejus Balčiūnas ◽  
Sarunas Svirskas ◽  
Martynas Kinka ◽  
Maciej Ptak ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Room Temperature ◽  
Structural Phase ◽  
Cubic Phase ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dielectric Relaxations ◽  
Broadband Dielectric Spectroscopy ◽  
Molecular Cation

<p>We use a multi-technique approach to determine the phase diagram and molecular cation dynamics of mixed methylammonium-formamidinium MA1-xFAxPbBr3 (0 ≤ x ≤ 1) hybrid perovskites. The calorimetric, ultrasonic and X-ray diffraction experiments show a substantial suppression of the structural phase transitions and stabilization of the cubic phase upon mixing. We use the broadband dielectric and Raman spectroscopies to study the MA and FA cations dynamics in these compounds. The broadband dielectric spectroscopy indicates absence of the MA cation ordering and a gradual increase of the rotation barrier upon mixing. The room-temperature dielectric permittivity substantially decreases as the fraction of the FA cations is increased. No significant changes of the permittivity are detected at temperatures where the dielectric relaxations are absent. We also observe weak signatures of a dipolar glass phase for the highest mixing level (x = 0.5). The Raman spectroscopy supports the dielectric results and reveals additional subtle information about the FA cation dynamics.</p><br>

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