scholarly journals Structural Evolution in the RE(OAc)3 · 2AcOH Structure Type. A Non-Linear, One-Dimensional Coordination Polymer with Unequal Interatomic Rare Earth Distances

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 768
Author(s):  
Markus Haase ◽  
Philipp Rissiek ◽  
Marianne Gather-Steckhan ◽  
Felix Henkel ◽  
Hans Reuter
Keyword(s):  
Acetic Acid ◽  
Rare Earth ◽  
Coordination Polymer ◽  
Structural Parameters ◽  
Linear Regression Analysis ◽  
Structural Evolution ◽  
Structure Type ◽  
One Dimensional ◽  
Coordination Modes ◽  
Non Linear

The existing range of the centrosymmetric, triclinic RE(OAc)3 · 2AcOH structure type has been extended for RE = Eu and Gd while the structure data of the Nd- and Sm-compounds have been revised and corrected, respectively, using low temperature (T = 100 K), well resolved (2θmax = 56°), highly redundant SCXRD data in order to evaluate the structural evolution within this class of acetic acid solvates by statistical methods. Within the nine-fold mono-capped square-antiprismatic coordination spheres of the RE3+ ions, RE-O distances decrease as a result of lanthanide contraction; some with different rates depending on the coordination modes (2.11/2.21) of the acetate ions. The experimental data show that the internal structural parameters of the acetate ions also correlate with their coordination modes. Both acetic acid molecules act as hydrogen bond donors but only one as monodentate ligand. The geometries of the hydrogen bonds reveal that they are strongly influenced by the size of the rare earth atom. The non-linear, one-dimensional coordination polymer propagates with unequal RE···RE distances along the a-axis. Rods of the coordination polymer are arranged in layers congruently stacked above each other with the hydrogen bonded acetic acid molecules as filler in between. In most cases, data fitting is best described in terms of a quadratic rather than a linear regression analysis.

Microstrain-assisted polymorphic phase transitions in (Eu1−x La x )2O3

2019 ◽  
Vol 52 (1) ◽  
pp. 32-39 ◽  
Author(s):  
K. A. Irshad ◽  
A. Saikumaran ◽  
V. Srihari ◽  
S. Kalavathi ◽  
N. V. Chandra Shekar
Keyword(s):  
Rare Earth ◽  
Phase Transitions ◽  
Structural Parameters ◽  
Structural Phase ◽  
Structural Evolution ◽  
Type Structure ◽  
X Ray Diffraction ◽  
The Difference ◽  
Rare Earth Sesquioxides ◽  
The Rare Earth

Solid solutions, (Eu1−x La x )2O3 (0 ≤ x ≤ 1), of the rare earth sesquioxides Eu2O3 and La2O3 have been prepared by a simple soft chemistry approach. The composition and morphology of the as-synthesized oxides have been characterized using energy-dispersive spectroscopy and scanning electron microscopy. The particles are of irregular shape and submicrometre size. In order to understand the structural evolution as a function of composition, angle-dispersive X-ray diffraction measurements have been carried out and the structural parameters have been obtained through Rietveld refinement. A structural phase transition from the cubic (C-type) to the monoclinic (B-type) structure and subsequently to the hexagonal (A-type) structure was observed with an increasing substitution of La. A detailed analysis of the transition boundaries in terms of the average cationic radius, R RE, shows that the onset of the C → B transition is at R RE = 0.980 Å, whereas the B → A transition occurs at R RE = 1.025 Å. A biphasic region of cubic and monoclinic structures is observed for 0.2 ≤ x ≤ 0.4 and one of monoclinic and hexagonal structures is observed for 0.5 ≤ x ≤ 0.6. The microstrain induced by the difference in size of the rare earth cations introduces a substitutional disorder in the crystal structure, which is a plausible cause of the observed phase transitions in these oxides.

scholarly journals Poly[[pentaaqua(μ4-pyridine-2,4,6-tricarboxylato)(μ3-pyridine-2,4,6-tricarboxylato)diterbium(III)] monohydrate]

2012 ◽  
Vol 68 (8) ◽  
pp. m1133-m1134 ◽  
Author(s):  
Xiao-Ke Yu ◽  
Hong-Lin Zhu
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Coordination Polymer ◽  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Tricarboxylic Acid ◽  
The Other ◽  
Coordination Modes ◽  
Trigonal Prismatic

The three-dimensional title coordination polymer, {[Tb2(C8H2NO6)2(H2O)5]·H2O}n, was hydrothermally synthesized by reacting the corresponding rare-earth salt with pyridine-2,4,6-tricarboxylic acid (H3ptc). There are two independent TbIIIatoms in the structure, one of which is nine-coordinated, forming a monocapped NO8square-antiprism and the other is eight-coordinated exhibiting a 4,4-bicapped NO7trigonal–prismatic environment. The complex units are interconnected through the ptc3−anions acting in different coordination modes, resulting in a three-dimensional coordination polymer. The crystal structure features extensive O—H...O hydrogen bonds.

Neue reduzierte Halogenide der Lanthanoide mit kondensierten Clustern: Tb6Br7 und Er6I7 / New Reduced Halides of Rare Earth Metals with Condensed Clusters: Tb6Br7 and Er6I7

1980 ◽  
Vol 35 (5) ◽  
pp. 626-630 ◽  
Author(s):  
Karl Berroth ◽  
Hansjürgen Mattausch ◽  
Arndt Simon
Keyword(s):  
Rare Earth ◽  
Rare Earth Metals ◽  
Structure Type ◽  
Space Group ◽  
One Dimensional ◽  
X Ray ◽  
Halogen Atoms ◽  
New Compounds ◽  
Structure Investigations

Abstract The new compounds Tb6Br7 and Er6I7 are formed from the trihalides with an excess of metal in sealed tantalum containers. X-ray structure investigations [space group C2/m; Tb6Br7 (Er6I7): a = 2057.1 (2137.5), b = 379.3 (386.9), c = 1180.0 (1231.9) pm, β = 124.59° (123.50°)] show one-dimensional regions connected by Ln-Ln bonds. The structure type can be described in terms of Ln6X12-clusters which are linked via edges of Ln6-octahedra to form double strings. The structure is derived from an FCC arrangement of halogen atoms part of which is systematically substituted by Ln6-octahedra.

scholarly journals Interaction of equivalence ratio fluctuations and flow fluctuations in acoustically forced swirl flames

2021 ◽  
pp. 175682772110155
Author(s):  
Vincent Kather ◽  
Finn Lückoff ◽  
Christian O. Paschereit ◽  
Kilian Oberleithner
Keyword(s):  
Equivalence Ratio ◽  
Transfer Functions ◽  
Transport Model ◽  
Mode Conversion ◽  
Fuel Injector ◽  
One Dimensional ◽  
Flow Fluctuations ◽  
Non Linear ◽  
Non Local ◽  
Acoustic Forcing

The generation and turbulent transport of temporal equivalence ratio fluctuations in a swirl combustor are experimentally investigated and compared to a one-dimensional transport model. These fluctuations are generated by acoustic perturbations at the fuel injector and play a crucial role in the feedback loop leading to thermoacoustic instabilities. The focus of this investigation lies on the interplay between fuel fluctuations and coherent vortical structures that are both affected by the acoustic forcing. To this end, optical diagnostics are applied inside the mixing duct and in the combustion chamber, housing a turbulent swirl flame. The flame was acoustically perturbed to obtain phase-averaged spatially resolved flow and equivalence ratio fluctuations, which allow the determination of flux-based local and global mixing transfer functions. Measurements show that the mode-conversion model that predicts the generation of equivalence ratio fluctuations at the injector holds for linear acoustic forcing amplitudes, but it fails for non-linear amplitudes. The global (radially integrated) transport of fuel fluctuations from the injector to the flame is reasonably well approximated by a one-dimensional transport model with an effective diffusivity that accounts for turbulent diffusion and dispersion. This approach however, fails to recover critical details of the mixing transfer function, which is caused by non-local interaction of flow and fuel fluctuations. This effect becomes even more pronounced for non-linear forcing amplitudes where strong coherent fluctuations induce a non-trivial frequency dependence of the mixing process. The mechanisms resolved in this study suggest that non-local interference of fuel fluctuations and coherent flow fluctuations is significant for the transport of global equivalence ratio fluctuations at linear acoustic amplitudes and crucial for non-linear amplitudes. To improve future predictions and facilitate a satisfactory modelling, a non-local, two-dimensional approach is necessary.

scholarly journals Copper(II) 2,2-Bis(Hydroxymethyl)Propionate Coordination Compounds with Hexamethylenetetramine: From Mononuclear Complex to One-Dimensional Coordination Polymer

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3358
Author(s):  
Sadaf Rauf ◽  
Agata Trzesowska-Kruszynska ◽  
Tomasz Sierański ◽  
Marcin Świątkowski
Keyword(s):  
Coordination Polymer ◽  
Coordination Compounds ◽  
Structural Diversity ◽  
Structural Features ◽  
Mononuclear Complex ◽  
Molar Ratio ◽  
One Dimensional ◽  
1D Coordination Polymer ◽  
Copper Coordination ◽  
Stretching Vibrations

Three new copper coordination compounds derived from 2,2-bis(hydroxymethyl)propionic acid (dmpa) and hexamethylenetetramine (hmta) were obtained and their crystal structures were determined. The stoichiometry of the reagents applied in the syntheses reflects the metal to ligand molar ratio in the formed solid products. Due to the multiple coordination modes of the used ligands, wide structural diversity was achieved among synthesized compounds, i.e., mononuclear [Cu(dmp)2(hmta)2(H2O)] (1), dinuclear [Cu2(dmp)4(hmta)2] (2), and 1D coordination polymer [Cu2(dmp)4(hmta)]n (3). Their supramolecular structures are governed by O—H•••O and O—H•••N hydrogen bonds. The compounds were characterized in terms of absorption (UV-Vis and IR) and thermal properties. The relationships between structural features and properties were discussed in detail. Owing to discrepancies in the coordination mode of a dmp ligand, bidentate chelating in 1, and bidentate bridging in 2 and 3, there is a noticeable change in the position of the bands corresponding to the stretching vibrations of the carboxylate group in the IR spectra. The differences in the structures of the compounds are also reflected in the nature and position of the UV-Vis absorption maxima, which are located at lower wavelengths for 1.

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