scholarly journals Structural Transformations in the Thermal Dehydration of [Cu2(bpa)(btec)(H2O)4]n Coordination Polymer

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1840
Author(s):  
Laura Bravo-García ◽  
Edurne S. Larrea ◽  
Beñat Artetxe ◽  
Luis Lezama ◽  
Juan M. Gutiérrez-Zorrilla ◽  
...  
Keyword(s):  
Variable Temperature ◽  
Microwave Assisted Synthesis ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Anhydrous Compound ◽  
Metal Organic ◽  
Coordination Water

Reactions between pyridinic ligands such as 1,2-bis(4-pyridyl)ethane (bpa) and transition metal cations are a very widespread technique to produce extended coordination polymers such as Metal-Organic Frameworks. In combination with a second ligand these systems could present different topologies and behaviors. In this context, the use of 1,2,4,5-benzenetetracarboxylic acid (H4btec) gave us a novel 2D compound, [Cu2(bpa)(btec)(H2O)4]n (1), which was prepared by microwave-assisted synthesis and structurally characterized by means of single crystal X-ray diffraction. Its thermal behavior was analyzed through thermogravimetric analysis and variable temperature powder X-ray diffraction, concluding that thermal stability is influenced by the coordination water molecules, allowing two sequential thermochromic phase transformations to take place. These transformations were monitored by electronic paramagnetic resonance spectroscopy and magnetic susceptibility measurements. In addition, the crystal structure of the anhydrous compound [Cu2(bpa)(btec)]n (1.ah) was determined. Finally, a topological study was carried out for the bpa ligand considering all the structures deposited in the Cambridge Structural Databased. More than 1000 structures were analyzed and classified into 17 different topologies, according to the role of the ligand.

Molecular reorientation in a dehydration process of an organic polar salt of 2,4-diaminotoluene/L(+)-tartaric acid

2017 ◽  
Vol 32 (1) ◽  
pp. 15-22
Author(s):  
Weicai Ju ◽  
Simin Qiu ◽  
Yaqiu Tao ◽  
Xiaodong Shen ◽  
Zhigang Pan
Keyword(s):  
Crystal Structures ◽  
Tartaric Acid ◽  
Variable Temperature ◽  
Ethanol Dehydration ◽  
X Ray Diffraction ◽  
Molecular Reorientation ◽  
X Ray ◽  
Hydrate Crystal ◽  
Dehydration Behavior

An organic polar hydrate was obtained through cocrystallization of 2,4-diaminotoluene (2,4-DAT) and L(+)-tartaric acid (TA) from ethanol. Dehydration behavior of the obtained hydrate was investigated using variable temperature powder X-ray diffraction (PXRD) and thermal analysis. Proton transfer from L(+)-TA to 2,4-DAT in both hydrate and dehydrated form was revealed via Fourier transform infrared spectroscopy. The crystal structures of both forms were determined using PXRD techniques. The similarities and differences between two crystal structures were analyzed and the role of water in the hydrate crystal structure was demonstrated.

scholarly journals Molecularly Engineered Lithium–Chromium Alkoxide for Selective Synthesis of LiCrO2 and Li2CrO4 Nanomaterials

Inorganics ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 22 ◽  
Author(s):  
Olusola Ojelere ◽  
David Graf ◽  
Sanjay Mathur
Keyword(s):  
Molecular Design ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Polymeric Chain ◽  
Mixed Metal Oxide ◽  
Resonance Spectroscopy ◽  
Selective Synthesis ◽  
X Ray Diffraction ◽  
Tem Analysis ◽  
Paramagnetic Resonance ◽  
X Ray

Achieving control over the phase-selective synthesis of mixed metal oxide materials remains a challenge to the synthetic chemist due to diffusion-driven growth, which necessitates the search for new compounds with pre-existent chemical bonds between the phase-forming elements. We report here a simple solvothermal process to fabricate LiCrO2 and Li2CrO4 nanoparticles from bimetallic single-source precursors, demonstrating the distinctive influence of molecular design and calcination conditions on the resulting nanomaterials. The chemical identity of [Li2Cr(OtBu)4Cl(THF)2] (1) and [LiCr(OtBu)2(PyCH=COCF3)2(THF)2] (2) was unambiguously established in the solid state by single-crystal X-ray diffraction, revealing the formation of a coordination polymeric chain in compound 1, whereas electron paramagnetic resonance spectroscopy (EPR) studies revealed a monomeric structure in solution. TEM analysis of synthesized LiCrO2 nanoparticles showed nearly uniform particles size of approximately 20 nm. The sensitivity of the LiCrO2 phase towards oxidation was investigated by X-ray diffraction, revealing the formation of the stable Li2CrO4 after calcination in air.

Persistent P-Stabilized Boryl Radicals with Bulky Substituents at Boron

Synthesis ◽  
2018 ◽  
Vol 50 (18) ◽  
pp. 3671-3678
Author(s):  
Didier Bourissou ◽  
Amos Rosenthal ◽  
Sonia Mallet-Ladeira ◽  
Ghenwa Bouhadir
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Room Temperature ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Radical Reactivity ◽  
Different Types ◽  
Electron Paramagnetic

Two new P-stabilized boryl radicals [Ph2P(naph)BAr] (Ar = Tip and Ter) have been prepared and characterized by electron paramagnetic resonance spectroscopy. These radicals are persistent for several days in solution at room temperature. The high steric congestion at boron does not prevent radical reactivity. Two different types of dimerization equilibrium have been observed. The structures of the dimers have been unambiguously established by X-ray diffraction crystallography.

scholarly journals Construction of C-C bonds via photoreductive coupling of ketones and aldehydes in the metal-organic-framework MFM-300(Cr)

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tian Luo ◽  
Lili Li ◽  
Yinlin Chen ◽  
Jie An ◽  
Chengcheng Liu ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance Spectroscopy ◽  
Metal Organic Framework ◽  
Photochemical Synthesis ◽  
Resonance Spectroscopy ◽  
Reductive Coupling ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
Aldehydes And Ketones ◽  
Metal Organic ◽  
Electron Paramagnetic

AbstractConstruction of C-C bonds via reductive coupling of aldehydes and ketones is hindered by the highly negative reduction potential of these carbonyl substrates, particularly ketones, and this renders the formation of ketyl radicals extremely endergonic. Here, we report the efficient activation of carbonyl compounds by the formation of specific host-guest interactions in a hydroxyl-decorated porous photocatalyst. MFM-300(Cr) exhibits a band gap of 1.75 eV and shows excellent catalytic activity and stability towards the photoreductive coupling of 30 different aldehydes and ketones to the corresponding 1,2-diols at room temperature. Synchrotron X-ray diffraction and electron paramagnetic resonance spectroscopy confirm the generation of ketyl radicals via confinement within MFM-300(Cr). This protocol removes simultaneously the need for a precious metal-based photocatalyst or for amine-based sacrificial agents for the photochemical synthesis.

X-RAY DIFFRACTION AND ELECTRON PARAMAGNETIC RESONANCE STUDIES OF A Bi4Sr2.5Ca2.5Cu4Ox SUPERCONDUCTING PHASE

1989 ◽  
Vol 03 (17) ◽  
pp. 1319-1325
Author(s):  
TH. LEVENTOURI ◽  
N. GUSKOS ◽  
M. CALAMIOTOU ◽  
O. PAPAGEORGIOU ◽  
S. PARASKEVAS ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Local Symmetry ◽  
Solid State Reaction Method ◽  
Superconducting Phase ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Electron Paramagnetic

We report a study of a low T c phase of the bismuth superconductor. A nominally Bi 4 Sr 2.5 Ca 2.5 Cu 4 O x compound was produced by the solid state reaction method with a T c = 80 K . X-ray diffraction studies show that the structure is very similar to the structure of the 4:3:3:4 composition with indications of small amounts of other phases. Electron paramagnetic resonance spectroscopy gives a strong Cu 2+ signal at temperatures above T c . We make a comparison between the local symmetry of the Cu 2+ ion complexes in this Bi sample and in the Y–Ba–Cu–O superconductor we had studied before.

Incorporation of Vanadium and Molybdenum into Yttrium-Arsenotungstates Supported by Amino Acid Ligands

2020 ◽  
Vol 73 (3) ◽  
pp. 137
Author(s):  
Fateme Akhlaghi Bagherjeri ◽  
Chris Ritchie ◽  
Robert W. Gable ◽  
Gary Bryant ◽  
Colette Boskovic
Keyword(s):  
Amino Acid ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Central Core ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Uv Visible ◽  
Visible Reflectance ◽  
Electron Paramagnetic

The preference for incorporation of molybdenum over tungsten into specific sites of a family of yttrium-arsenotungstates with amino acid ligands prompted exploration of the incorporation of other metals, affording three new vanadium-containing (V/W and V/Mo/W) analogues: K2(GlyH)10[As4(V2W2)W44Y4O160(Gly)8(H2O)12]·11Gly (1), (MBAH)9(L-NleH)3[As4(V2W2)W44Y4O160(L-Nle)8(H2O)12] (2), and (MBAH)9(L-NleH)3[As4(V2W2)Mo2W42Y4O160(L-Nle)8(H2O)12] (3) (Gly=glycine and L-Nle=l-norleucine, MBAH=4-methylbenzylammonium). These hybrid polyoxometalates all possess a tetrametallic oxo-bridged {VIV2WVI2} central core surrounded by an amino acid-ligated cyclic metal-oxo framework. X-Ray photoelectron, UV-visible reflectance, and electron paramagnetic resonance spectroscopy, together with metal analysis, confirm the incorporation of vanadium into the polyoxometalates, while single crystal X-ray diffraction analysis supports the location of the vanadium atoms in the central core.

scholarly journals Influence of MoS2 on Activity and Stability of Carbon Nitride in Photocatalytic Hydrogen Production

Catalysts ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 695 ◽  
Author(s):  
Ramesh P. Sivasankaran ◽  
Nils Rockstroh ◽  
Carsten R. Kreyenschulte ◽  
Stephan Bartling ◽  
Henrik Lund ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Composite Photocatalysts ◽  
Electron Transfer Properties ◽  
Electron Paramagnetic

MoS2/C3N4 (MS-CN) composite photocatalysts have been synthesized by three different methods, i.e., in situ-photodeposition, sonochemical, and thermal decomposition. The crystal structure, optical properties, chemical composition, microstructure, and electron transfer properties were investigated by X-ray diffraction, UV-vis diffuse reflectance spectroyscopy, X-ray photoelectron spectroscopy, electron microscopy, photoluminescence, and in situ electron paramagnetic resonance spectroscopy. During photodeposition, the 2H MoS2 phase was formed upon reduction of [MoS4]2− by photogenerated conduction band electrons and then deposited on the surface of CN. A thin crystalline layer of 2H MoS2 formed an intimate interfacial contact with CN that favors charge separation and enhances the photocatalytic activity. The 2H MS-CN phase showed the highest photocatalytic H2 evolution rate (2342 μmol h−1 g−1, 25 mg catalyst/reaction) under UV-vis light irradiation in the presence of lactic acid as sacrificial reagent and Pt as cocatalyst.

Metal–organic framework in an l-arginine copper(ii) ion polymer: structure, properties, theoretical studies and microbiological activity

RSC Advances ◽  
2015 ◽  
Vol 5 (46) ◽  
pp. 36295-36306 ◽  
Author(s):  
Agnieszka Wojciechowska ◽  
Anna Gągor ◽  
Wiktor Zierkiewicz ◽  
Anna Jarząb ◽  
Agnieszka Dylong ◽  
...  
Keyword(s):  
Uv Spectroscopy ◽  
Metal Organic Framework ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Metal Organic ◽  
Ft Ir ◽  
Electron Paramagnetic ◽  
Microbiological Properties ◽  
Structure Properties

A novel 1D polymeric copper(ii) complex of formula {[Cu(l-Arg)2(μ-4,4′-bpy)]Cl2·3H2O∞} was synthesized and characterized using X-ray diffraction, FT-IR, Raman, electron paramagnetic resonance and NIR-vis-UV spectroscopy, and its microbiological properties were analyzed.

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