Size Matters: New Zintl Phase Hydrides of REGa (RE = Y, La, Tm) and RESi (RE = Y, Er, Tm) with Large and Small Cations

Many Zintl phases exhibiting a CrB type structure form hydrides. Systematic studies of AeTtHx (Ae = Ca, Sr, Ba; Tt = Si, Ge, Sn), LnTtHx (Ln = La, Nd; Tt = Si, Ge, Sn), and LnGaHx (Ln = Nd, Gd) showed the vast structural diversity of these systems. Hydrogenation reactions on REGa (RE = Y, La, Tm) and RESi (RE = Y, Er, Tm) were performed in steel autoclaves under hydrogen pressure up to 5 MPa and temperatures up to 773 K. The products were analyzed by X-ray and neutron powder diffraction. RESi (RE = Y, Er, Tm) form hydrides in the C-LaGeD type. LaGaD1.66 is isostructural to NdGaD1.66 and shows similar electronic features. Ga-D distances (1.987(13) Å and 2.396(9) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. In TmGaD0.93(2) with a distorted CrB type structure deuterium atoms exclusively occupy tetrahedral voids. Theoretical calculations on density functional theory (DFT) level confirm experimental results and suggest metallic properties for the hydrides.

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Different Cerium Valence Transitions Observed by Hydrogenation of the Ternary Germanides CeRhGe and CeIrGe – Structure, Physical Properties and Chemical Bonding

Zeitschrift für Naturforschung B ◽

10.1515/znb-2008-0615 ◽

2008 ◽

Vol 63 (6) ◽

pp. 685-694 ◽

Cited By ~ 8

Author(s):

Bernard Chevalier ◽

Etienne Gaudin ◽

Adel F. Al Alam ◽

Samir F. Matar ◽

François Weill ◽

...

Keyword(s):

Electronic Structures ◽

Density Functional ◽

Spin Fluctuation ◽

Type Structure ◽

Kondo Temperature ◽

Intermediate Valence ◽

Functional Theory ◽

X Ray ◽

Transmission Electron ◽

Power Measurements

The ternary germanides CeRhGe and CeIrGe which crystallize in the orthorhombic TiNiSi-type structure, absorb hydrogen at 523 K. X-Ray powder diffraction and transmission electron microscopy indicate that the hydrides CeRhGeH1.8 and CeIrGeH1.8 adopt the hexagonal ZrBeSi-type structure. Magnetization, electrical resistivity and thermoelectric power measurements reveal that these hydrides are intermediate-valence compounds. An unusual transition from antiferromagnetic to spin fluctuation behavior occurs upon hydrogenation of CeRhGe, while on the contrary, CeIrGeH1.8 presents a Kondo temperature of 285 K smaller than that observed for CeIrGe (610 K). In order to explain these opposite valence transitions, the electronic structures of the hydrides have been selfconsistently calculated within the local spin density functional theory (LSDF). The structures are compared to those reported previously by us for CeRhGe and CeIrGe.

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Hydrogenation Properties of LnAl2 (Ln = La, Eu, Yb), LaGa2, LaSi2 and the Crystal Structure of LaGa2H0.71(2)

Crystals ◽

10.3390/cryst9040193 ◽

2019 ◽

Vol 9 (4) ◽

pp. 193 ◽

Cited By ~ 4

Author(s):

Anton Werwein ◽

Christopher Benndorf ◽

Marko Bertmer ◽

Alexandra Franz ◽

Oliver Oeckler ◽

...

Keyword(s):

Nmr Spectroscopy ◽

Density Functional ◽

Theoretical Calculations ◽

Hydrogen Gas ◽

Hydrogen Atoms ◽

Zintl Phases ◽

Trigonal Bipyramidal ◽

Transmission Electron ◽

Hydrogenation Reactions ◽

Lanthanide Metals

Many Zintl phases take up hydrogen and form hydrides. Hydrogen atoms occupy interstitial sites formed by alkali or alkaline earth metals and / or bind covalently to the polyanions. The latter is the case for polyanionic hydrides like SrTr2H2 (Tr = Al, Ga) with slightly puckered honeycomb-like polyanions decorated with hydrogen atoms. This study addresses the hydrogenation behavior of LnTr2, where the lanthanide metals Ln introduce one additional valence electron. Hydrogenation reactions were performed in autoclaves and followed by thermal analysis up to 5.0 MPa hydrogen gas pressure. Products were analyzed by powder X-ray and neutron diffraction, transmission electron microscopy, and NMR spectroscopy. Phases LnAl2 (Ln = La, Eu, Yb) decompose into binary hydrides and aluminium-rich intermetallics upon hydrogenation, while LaGa2 forms a ternary hydride LaGa2H0.71(2). Hydrogen atoms are statistically distributed over two kinds of trigonal-bipyramidal La3Ga2 interstitials with 67% and 4% occupancy, respectively. Ga-H distances (2.4992(2) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. 2H solid-state NMR spectroscopy and theoretical calculations on Density Functional Theory (DFT) level confirm that LaGa2H0.7 is a typical interstitial metallic hydride.

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Sr(Hg1–xSnx)4: variations of the EuIn4-type structure

Zeitschrift für Naturforschung B ◽

10.1515/znb-2015-0004 ◽

2015 ◽

Vol 70 (4) ◽

pp. 265-277

Author(s):

Marco Wendorff ◽

Caroline Röhr

Keyword(s):

Density Functional ◽

Valence Electron ◽

Theoretical Study ◽

Building Blocks ◽

Type Structure ◽

Intermediate Valence ◽

Model Compounds ◽

Functional Theory ◽

X Ray ◽

Successive Substitution

AbstractStarting from the new compound SrHg2Sn2, which is isoelectronic and also isotypic to the indide SrIn4, the successive substitution of Sn against the electron poor Hg has been investigated in a combined synthetic, crystallographic, and bond-theoretical study. Along the 1:4 section Sr(Hg1–xSnx)4 a series of compounds with Sn contents x between 0.5 and 0.2 were synthesized from stoichiometric ratios of the elements. Their crystal structures, which represent three different variants of the EuIn4-type structure, have been determined using single crystal X-ray data. The most electron rich compound SrHg2Sn2 crystallizes in the original EuIn4-type [monoclinic, C2/m, a = 1257.9(14), b = 490.1(4), c = 997.8(12) pm, β = 117.60(6)°, Z = 4, R1 = 0.0838], with a fully ordered Hg and Sn distribution. The four atom sites form two different folded ladders with an alternating Hg/Sn distribution. Like in the KHg2-type, the ladders are connected via six-membered rings. In between, double tubes with an internal Sn–Sn bond are connected via further Sn–Sn bonds to form sheets similar to those observed in SiAs. The most electron-poor phase SrHg3.2Sn0.8 crystallizes in a strongly distorted variant of this structure [a = 1172.8(4), b = 497.9(2), c = 1010.0(4) pm, β = 118.860(7)°, Z = 4, R1 = 0.0549]. Herein, additional Hg–Hg bonds are formed, and the open tubes are distorted into rods of edge-sharing rhombohedra resembling the structure motifs of elemental Hg. At an intermediate valence electron (v.e.) number, i.e., in SrHg2.5Sn1.5, an isomorphous tripled superstructure (a = 2704.4(5), b = 493.87(7), c = 1197.1(2) pm, β = 90.838(14)°, Z = 12, R1 = 0.0475) occurs, where the building blocks of the two variants of the EuIn4-type structure alternate in a 1:2 ratio. The bonding situation and the “coloring,” i.e., the Hg/Sn distribution in the polyanionic network, are discussed considering the different sizes of the atoms and the charge distribution (Bader AIM charges), which has been calculated within the framework of the FP-LAPW density functional theory for SrHg2Sn2 and the model compounds “SrHg3Sn” and “SrHg4.”

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X-ray molecular structure and theoretical study of 1,4-bis[2-cyano-2-(o-pyridyl)ethenyl]benzene

Chemical Papers ◽

10.2478/s11696-013-0434-5 ◽

2014 ◽

Vol 68 (2) ◽

Cited By ~ 2

Author(s):

M. Percino ◽

Maria Castro ◽

Margarita Ceron ◽

Guillermo Soriano-Moro ◽

Victor Chapela ◽

...

Keyword(s):

Density Functional ◽

Theoretical Calculations ◽

Chloroform Solution ◽

Monoclinic System ◽

Functional Theory ◽

Torsion Angles ◽

X Ray ◽

Structural Characterisation ◽

Phenyl Rings ◽

Moller Plesset

AbstractThe structural characterisation of the molecule 1,4-bis[2-cyano-2-(o-pyridyl)ethenyl] benzene obtained through Knoevenagel condensation is reported. The single crystals, as light brown rods, were cultured from a chloroform solution using a slow evaporation method at ambient temperature. The compound crystallised in the monoclinic system belonging to the C2/c space group with a = 26.4556(9) Å, b = 3.73562(10) Å, c = 18.4230(6) Å, β = 109.841(4)° and the asymmetric unit comprising Z = 4. The structure is ordered and the molecules of the title compound exhibited a lattice with water molecules located at sites of inversion and two-fold axial symmetries. Thus, only halves of the molecules are symmetrically independent. The lattice is reported and contrasted with X-ray single-crystal diffraction and theoretical calculations of 1,4-bis(1-cyano-2-phenylethenyl)benzene. By using density functional theory (DFT) and second order Moller-Plesset (MP2) theoretical calculations, the ground state geometry in the whole molecule at the B3LYP/6-31+G(d,p), and MP2/6-31+G(d,p) theory levels, respectively, were optimised. The DFT calculations showed a quasi-planar structure of the molecule, whereas the wave function-based MP2 method afforded a non-planar optimised structure with significant torsion angles between the pyridine and phenyl rings.

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Conformational and structural diversity of iridium dimethyl sulfoxide complexes

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520617011490 ◽

2017 ◽

Vol 73 (6) ◽

pp. 1032-1042 ◽

Cited By ~ 2

Author(s):

Benjamin M. Ridgway ◽

Ana Foi ◽

Rodrigo S. Corrêa ◽

Damian E. Bikiel ◽

Javier Ellena ◽

...

Keyword(s):

Dimethyl Sulfoxide ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Structural Diversity ◽

Stable Form ◽

Functional Theory ◽

X Ray ◽

X Ray Crystallography ◽

Conformational Preferences ◽

Clinically Significant

Transition metal complexes containing dimethyl sulfoxide (DMSO) are important precursors in catalysis and metallodrugs. Understanding the solid-state supramolecular structure is crucial for predicting the properties and biological activity of the material. Several crystalline phases of DMSO-coordinated iridium anions with different cations, potassium (1a) and n-butylammonium (1b), were obtained and their structures determined by X-ray crystallography. Compound (1a) is present in two solvatomorphic forms: α and β; the β form contains disordered solvent water. In addition, the structures exhibit different rotamers of the trans-[IrCl4(DMSO)2]− anion with the trans-DMSO ligands being oriented in anti and gauche conformations. In consideration of these various conformers, the effects of the crystallized solvent and intermolecular interactions on the conformational preferences of the anion are discussed. In addition, density functional theory calculations were used to investigate the energies of the anions in the different conformations. It was found that hydrogen bonds between water and the DMSO complex stabilize the gauche conformation which is the least stable form of the trans-DMSO complex. Consequently, by controlling the number of hydrogen-bond donors and acceptors and the amount of water, it may be possible to obtain different solvatomorphs of clinically significant metallodrugs.

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Synthesis of Pure NiTiSn by Mechanical Alloying: An Investigation of the Optimal Experimental Conditions Supported by First Principles Calculations

Metals ◽

10.3390/met8100835 ◽

2018 ◽

Vol 8 (10) ◽

pp. 835 ◽

Cited By ~ 3

Author(s):

Monique Tillard ◽

Alexandre Berche ◽

Philippe Jund

Keyword(s):

Mechanical Alloying ◽

Density Functional ◽

Annealing Temperature ◽

Theoretical Calculations ◽

First Principles Calculations ◽

X Ray Diffraction ◽

Experimental Conditions ◽

Functional Theory ◽

X Ray ◽

Careful Investigation

Synthesis of NiTiSn by a mechanical alloying process followed by a high temperature thermal annealing was studied. Experiments were conducted varying parameters like the provided energy, the mechanical alloying reaction time, as well as the annealing temperature and duration. Based on the careful investigation of the phases present in the samples by systematic X-ray diffraction (after mechanical alloying and after annealing) and selected microscopy analyses, a reaction mechanism is proposed supported by theoretical calculations at the DFT (Density Functional Theory) level. An energy window to prepare directly NiTiSn has been evidenced. Highly pure NiTiSn has also been obtained by conversion from a multicomponent precursor obtained by low energy mechanical alloying.

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Tracking the dissolution–recrystallization structural transformation (DRST) of copper(II) complexes: a combined crystallographic, mass spectrometric and DFT study

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229620006701 ◽

2020 ◽

Vol 76 (7) ◽

pp. 655-662

Author(s):

Qian-Jun Deng ◽

Min Chen ◽

Dong-Chu Chen ◽

Hang-Yu Long ◽

Chang-Ai Chen

Keyword(s):

Mass Spectrometry ◽

Structural Transformation ◽

Density Functional ◽

Electrospray Mass Spectrometry ◽

Theoretical Calculations ◽

Binuclear Copper ◽

Functional Theory ◽

X Ray ◽

X Ray Crystallography ◽

First Time

Methanol- and temperature-induced dissolution–recrystallization structural transformation (DRST) was observed among two novel CuII complexes. This is first time that the combination of X-ray crystallography, mass spectrometry and density functional theory (DFT) theoretical calculations has been used to describe the fragmentation and recombination of a mononuclear CuII complex at 60 °C in methanol to obtain a binuclear copper(II) complex. Combining time-dependent high-resolution electrospray mass spectrometry, we propose a possible mechanism for the conversion of bis(8-methoxyquinoline-κ2 N,O)bis(thiocyanato-κN)copper(II), [Cu(NCS)2(C10H9NO)2], Cu1, to di-μ-methanolato-κ4 O:O-bis[(8-methoxyquinoline-κ2 N,O)(thiocyanato-κN)copper(II)], [Cu2(CH3O)2(NCS)2(C10H9NO)2], Cu2, viz. [Cu(SCN)2(L)2] (Cu1) → [Cu(L)2] → [Cu(L)]/L → [Cu2(CH3O)2(NCS)2(L)2] (Cu2). We screened the antitumour activities of L (8-methoxyquinoline), Cu1 and Cu2 and found that the antiproliferative effect of Cu2 on some tumour cells was much greater than that of L and Cu1.

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Theoretical and Experimental Evaluation of the Effect of Fluorinated Substituent on the Topological Landscape and Thermodynamic Stability of Zeolitic Imidazolate Framework Polymorphs

10.26434/chemrxiv.7072577.v1 ◽

2018 ◽

Author(s):

Mihails Arhangelskis ◽

Athanassis Katsenis ◽

Novendra Novendra ◽

Zamirbek Akimbekov ◽

Dayaker Gandrath ◽

...

Keyword(s):

Density Functional Theory ◽

Mechanochemical Synthesis ◽

Thermodynamic Stability ◽

Experimental Evaluation ◽

Density Functional ◽

Theoretical Calculations ◽

Zeolitic Imidazolate Framework ◽

Functional Theory ◽

Calorimetric Measurements ◽

And Calorimetry

By combining mechanochemical synthesis and calorimetry with theoretical calculations, we demonstrate that dispersion-corrected periodic density functional theory (DFT) can accurately survey the topological landscape and predict relative energies of polymorphs for a previously inaccessible fluorine-substituted zeolitic imidazolate framework (ZIF). Experimental screening confirmed two out of three theoretically anticipated polymorphs, and the calorimetric measurements provided an excellent match to theoretically calculated energetic difference between them.<br>

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Highly Electron-Deficient Pyridinium-Nitrones for Rapid and Tunable Inverse-Electron-Demand Strain-Promoted Alkyne-Nitrone Cycloaddition to Bicyclo[6.1.0]nonyne

10.26434/chemrxiv.8251370 ◽

2019 ◽

Author(s):

Praveen Gunawardene ◽

Wilson Luo ◽

Alexander M. Polgar ◽

John F. Corrigan ◽

Mark Workentin

Keyword(s):

Density Functional Theory ◽

Reaction Kinetics ◽

Density Functional ◽

Functional Theory ◽

X Ray ◽

Inverse Electron Demand ◽

X Ray Crystallography ◽

Electron Demand

<div> <div> <p>Highly accelerated inverse-electron-demand strain-promoted alkyne-nitrone cycloaddition (IED SPANC) between a sta- ble cyclooctyne (bicyclo[6.1.0]nonyne (BCN)) and nitrones delocalized into a Cα-pyridinium functionality is reported, with the most electron-deficient “pyridinium-nitrone” displaying among the most rapid cycloadditions to BCN that is currently reported. Density functional theory (DFT) and X-ray crystallography are explored to rationalize the effects of N- and Cα-substituent modifications at the nitrone on IED SPANC reaction kinetics and the overall rapid reactivity of pyridinium-delocalized nitrones.</p> </div> </div>

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