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Solid-state NMR

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https://www.readbyqxmd.com/read/28543928/li12p3n9-with-non-condensed-p3n9-12-rings-and-its-high-pressure-polymorph-li4pn3-with-infinite-chains-of-pn4-tetrahedra
#1
Wolfgang Schnick, Robin Niklaus, Eva-Maria Bertschler
Li12P3N9 was synthesized by solid-state reaction of Li3N and P3N5 at 790 °C. It is made up of non-condensed [P3N9]12- dreier-rings of PN4-tetrahedra. The high-pressure polymorph Li4PN3 of the latter was synthesized under high-pressure/high-temperature conditions from Li12P3N9 or LiPN2 and Li7PN4 at 6 or 7 GPa, respectively, using multianvil technique. Li4PN3 is the first lithium catena-nitridophosphate and contains PN3 zweier-chains of corner sharing PN4-tetrahedra. To confirm the structure elucidated from single-crystal X-ray data, Rietveld refinement, 6Li, 7Li and 31P solid-state NMR, FTIR spectroscopy and EDX measurements were carried out...
May 23, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28540968/synthetic-and-structural-studies-of-phosphine-coordinated-boronium-salts
#2
Anthony F Hill, Jas S Ward
The reaction of BrH2B·SMe2 with primary and secondary phosphines affords a range of boronium salts of the form [H2B(PR3)2]Br (PR3 = PHCy21; PHPh2, 2; PH2Cy, 3), which have been fully characterised including solid-state determinations. Reactions of bulky tertiary phosphines, e.g., PCy3 and PPh3, with BrH2B·SMe2 do not proceed beyond the phosphine-stabilised bromoborane adducts, however, the smaller tertiary phosphine PMe2Ph readily proceeds to form [H2B(PMe2Ph)2]Br (4). The formation of the unsymmetrical boronium salts [H2B(PH2Cy)(PHCy2)]Br (5) and [H2B(PHCy2)(PHPh2)]Br (6) was observed by in situ NMR spectroscopy, however, the compounds were found to spontaneously disproportionate to their respective homophosphine boronium cations, even on prolonged storage in solution at -78 °C...
May 25, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28539702/one-step-synthesis-of-hierarchical-zsm-5-using-cetyltrimethylammonium-as-mesoporogen-and-structure-directing-agent
#3
Lingqian Meng, Brahim Mezari, Maarten G Goesten, Emiel J M Hensen
Hierarchical ZSM-5 zeolite is hydrothermally synthesized in a single step with cetyltrimethylammonium (CTA) hydroxide acting as mesoporogen and structure-directing agent. Essential to this synthesis is the replacement of NaOH with KOH. An in-depth solid-state NMR study reveals that, after early electrostatic interaction between condensed silica and the head group of CTA, ZSM-5 crystallizes around the structure-directing agent. The crucial aspect of using KOH instead of NaOH lies in the faster dissolution of silica, thereby providing sufficient nutrients for zeolite nucleation...
May 9, 2017: Chemistry of Materials: a Publication of the American Chemical Society
https://www.readbyqxmd.com/read/28537719/synthesis-and-characterization-of-the-lithium-rich-phosphidosilicates-li10si2p6-and-li3si3p7
#4
Henrik Eickhoff, Lorenzo Toffoletti, Wilhelm Klein, Gabriele Raudaschl-Sieber, Thomas F Fässler
The lithium phosphidosilicates Li10Si2P6 and Li3Si3P7 are obtained by high-temperature reactions of the elements or including binary Li-P precursors. Li10Si2P6 (P21/n, Z = 2, a = 7.2051(4) Å, b = 6.5808(4) Å, c = 11.6405(7) Å, β = 90.580(4)°) features edge-sharing SiP4 double tetrahedra forming [Si2P6](10-) units with a crystal structure isotypic to Na10Si2P6 and Na10Ge2P6. Li3Si3P7 (P21/m, Z = 2, a = 6.3356(4) Å, b = 7.2198(4) Å, c = 10.6176(6) Å, β = 102.941(6)°) crystallizes in a new structure type, wherein SiP4 tetrahedra are linked via common vertices and which are further connected by polyphosphide chains to form unique ∞(2)[Si3P7](3-) double layers...
May 24, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28537407/8-propyldithieno-3-2-b-2-3-e-pyridine-3-5-diamine-ditipiram-derivatives-as-neutral-receptors-tailored-for-binding-of-carboxylates
#5
Agnieszka Cholewiak, Agnieszka Tycz, Janusz Jurczak
The DITIPIRAM (8-propyldithieno[3,2-b:2',3'-e]pyridine-3,5-diamine)-based receptors 11 and 12 were readily synthesized, and their anion-binding properties were studied both in solution and in the solid-state. (1)H NMR titrations revealed that receptor 12 equipped with two phenyl-urea groups preferentially binds carboxylates, even in the highly competitive DMSO-d6/CD3OH solvent mixture. X-ray analysis showed that receptor 12 exhibited great complementarity for benzoate, which is cooperatively bound by the means of four highly directional hydrogen bonds from the two urea groups...
May 24, 2017: Organic Letters
https://www.readbyqxmd.com/read/28537394/3d-double-quantum-double-quantum-exchange-spectroscopy-of-protons-under-100-khz-magic-angle-spinning
#6
Rongchun Zhang, Nghia Tuan Duong, Yusuke Nishiyama, Ayyalusamy Ramamoorthy
Solid-state 1H NMR spectroscopy has attracted much attention in the recent years due to the remarkable spectral resolution improvement by ultrafast magic-angle-spinning (MAS) as well as due to the sensitivity enhancement rendered by proton detection. Although these developments have enabled the investigation of a variety of challenging chemical and biological solids, the proton spectral resolution is still poor for many rigid solid systems owing to the presence of conformational heterogeneity and the unsuppressed residual proton-proton dipolar couplings even with the use of the highest currently feasible sample spinning speed of ~130 kHz...
May 24, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28537393/paramagnetic-properties-of-a-crystalline-iron-sulfur-protein-by-magic-angle-spinning-nmr-spectroscopy
#7
Andrea Bertarello, Tobias Schubeis, Carmelo Fuccio, Enrico Ravera, Marco Fragai, Giacomo Parigi, Lyndon Emsley, Guido Pintacuda, Claudio Luchinat
We present the first solid-state NMR study of an iron-sulfur protein. The combined use of very fast (60 kHz) magic-angle spinning and tailored radiofrequency irradiation schemes allows the detection and the assignment of most of the (1)H and (13)C resonances of the oxidized high-potential iron-sulfur protein I from Ectothiorhodospira halophila (EhHiPIP I), including those in residues coordinating the Fe4S4 cluster. For these residues, contact shifts as large as 100 and 400 ppm for (1)H and (13)C resonances, respectively, were observed, which represent the most shifted solid-state NMR signals ever measured in metalloproteins...
May 24, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28537272/fibril-polymorphism-affects-immobilized-non-amyloid-flanking-domains-of-huntingtin-exon1-rather-than-its-polyglutamine-core
#8
Hsiang-Kai Lin, Jennifer C Boatz, Inge E Krabbendam, Ravindra Kodali, Zhipeng Hou, Ronald Wetzel, Amalia M Dolga, Michelle A Poirier, Patrick C A van der Wel
Polyglutamine expansion in the huntingtin protein is the primary genetic cause of Huntington's disease (HD). Fragments coinciding with mutant huntingtin exon1 aggregate in vivo and induce HD-like pathology in mouse models. The resulting aggregates can have different structures that affect their biochemical behaviour and cytotoxic activity. Here we report our studies of the structure and functional characteristics of multiple mutant htt exon1 fibrils by complementary techniques, including infrared and solid-state NMR spectroscopies...
May 24, 2017: Nature Communications
https://www.readbyqxmd.com/read/28535993/structural-basis-for-asymmetric-conductance-of-the-influenza-m2-proton-channel-investigated-by-solid-state-nmr-spectroscopy
#9
Venkata S Mandala, Shu Yu Liao, Byungsu Kwon, Mei Hong
The influenza M2 protein forms an acid-activated proton channel that is essential for virus replication. The transmembrane H37 selects for protons under low external pH (pHout) while W41 ensures proton conduction only from the N-terminus to the C-terminus and prevents reverse current under low internal pH (pHin). Here we address the molecular basis for this asymmetric conduction by investigating the structure and dynamics of a mutant channel, W41F, which permits reverse current under low pHin. Solid-state NMR experiments show that W41F M2 retains the pH-dependent α-helical conformations and tetrameric structure of the wild-type channel, but has significantly altered protonation and tautomeric equilibria at H37...
May 20, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28535056/solid-state-nmr-structure-based-inhibitor-design-to-achieve-selective-inhibition-of-the-parallel-in-register-%C3%AE-sheet-versus-antiparallel-iowa-mutant-%C3%AE-amyloid-fibrils
#10
Qinghui Cheng, Wei Qiang
Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has been widely applied to characterize the high-resolution structures of β-amyloid (Aβ) fibrils. While these structures provide crucial molecular insights on the deposition of amyloid plaques in Alzheimer's diseases (AD), ssNMR structures have been rarely used so far as basis for designing inhibitors. It remains a challenge because the ssNMR-based Aβ fibrils structures were usually obtained with sparsely-isotope-labeled peptides with limited experimental constraints, where the structural models, especially the side-chain coordinates showed restricted precision...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28534619/quantitative-solid-state-nmr-study-on-ligand-surface-interaction-in-cysteine-capped-cdse-magic-sized-clusters
#11
Takuya Kurihara, Yasuto Noda, Kiyonori Takegoshi
Ligand-surface interaction of semiconductor nanoparticles (NPs) controls their optoelectronic properties, and thus examinations of the interaction are essential for the nanoelectronic applications of NPs. Herein, solid-state nuclear magnetic resonance (NMR) is performed to unravel the ligand-surface interaction in cysteine-capped CdSe magic-sized clusters. (15)N-(113)Cd through-bond J-filtered NMR directly shows the presence of the nitrogen-cadmium chemical bond for the first time and indicates that ~43% of the amines form the chemical bond...
May 23, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28534573/solvent-dependent-nuclearity-geometry-and-catalytic-activity-of-sphos-pd-ph-cl-2
#12
John B Brazier, Mark A Newton, Elena M Barreiro, Luis A Adrio, Leticia Naya, King Kuok Mimi Hii
The nuclearity and structures of the palladium complex [(SPhos)Pd(Ph)Cl]2 in the solid and solution states are revisited using a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, NMR spectroscopy, mass spectrometry, DFT calculations and trapping experiments. The complex was tested for its catalytic activity in the coupling reaction between chlorobenzene and n-hexylamine, where different deactivation behaviours were observed in toluene, 1,4-dioxane and DMF.
May 23, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28534299/adsorption-onto-mesoporous-silica-using-supercritical-fluid-technology-improves-dissolution-rate-of-carbamazepine-a-poorly-soluble-compound
#13
Aditya V Gandhi, Priyanka Thipsay, Bharat Kirthivasan, Emilio Squillante
The purpose of this research was to design and characterize an immediate-release formulation of carbamazepine (CBZ), a poorly soluble anti-epileptic drug, using a porous silica carrier. Carbon dioxide in its supercritical state (2000 psi, 30-35°C) was used as an anti-solvent to precipitate CBZ onto two particle size variants of silica. Adsorption isotherms were used as a pre-formulation strategy to select optimum ratios of silica and CBZ. The obtained drug-silica formulations were characterized by dissolution studies, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM)...
May 22, 2017: AAPS PharmSciTech
https://www.readbyqxmd.com/read/28529775/crystal-structure-and-hirshfeld-surface-analysis-of-the-new-cyclo-diphosphazane-etnp-s-nme2-2
#14
Chokri Issaoui, Hammouda Chebbi, Khaled Alouani, Abderrahmen Guesmi
The cyclic compound 2,4-bis(dimethylamino)-1,3-diethylcyclodiphosphazane-2,4-dithione [systematic name: 2,4-bis(dimethylamino)-1,3-diethyl-1,3,2λ(5),4λ(5)-diazadiphosphetidine-2,4-dithione], C8H22N4P2S2 or [EtNP(S)NMe2]2, is member of a class of mol-ecules that may be used, by virtue of their complexation properties, for the extraction of metals. This compound was characterized in solution by ((1)H and (31)P) NMR, and in the solid state by energy-dispersive X-ray spectroscopy (EDX) and by X-ray crystallography...
May 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
https://www.readbyqxmd.com/read/28527462/low-power-broadband-solid-state-mas-nmr-of-14-n
#15
Andrew J Pell, Kevin J Sanders, Sebastian Wegner, Guido Pintacuda, Clare P Grey
We propose two broadband pulse schemes for (14)N solid-state magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) that achieves (i) complete population inversion and (ii) efficient excitation of the double-quantum spectrum using low-power single-sideband-selective pulses. We give a comprehensive theoretical description of both schemes using a common framework that is based on the jolting-frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983)]. This formalism is used to determine for the first time that we can obtain complete population inversion of (14)N under low-power conditions, which we do here using single-sideband-selective adiabatic pulses...
May 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28524206/co2-adsorption-on-different-organo-modified-sba-15-silicas-a-multidisciplinary-study-on-the-effects-of-basic-surface-groups
#16
G Gatti, D Costenaro, C Vittoni, G Paul, V Crocellà, E Mangano, S Brandani, S Bordiga, M Cossi, L Marchese, C Bisio
Hybrid organic-inorganic SBA-15 silicas functionalized with increasing amounts of amino groups were studied in this work aiming to evaluate the effects of their physico-chemical properties on CO2 capture ability. Three different amino-silane species were used: 3-aminopropyltriethoxysilane (APTS), 3-(2-aminoethyl)aminopropyltrimethoxysilane (EAPTS) and 3-[2-(2-aminoethyl)aminoethyl] aminopropyltrimethoxysilane (PAPTS). More specifically, samples were prepared by using two methods, following a post-synthesis grafting procedure and a one-pot preparation method...
May 19, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28521205/preparation-and-characterization-of-a-novel-macroporous-silica-bipyridine-asymmetric-multidentate-functional-adsorbent-and-its-application-for-heavy-metal-palladium-removal
#17
Lei Xu, Anyun Zhang, Fengmei Zhang, Jiyong Liu
The effective removal of heavy metal (107)Pd(II) from highly active liquid waste (HLW) is very valuable for reducing its hazardous and risk to public health and environment. For this purpose, a novel silica-bipyridine multidentate functional adsorbent was synthesized by vacuum infusing a new asymmetric N-donor ligand CA-MTBP (bipyridine derivative) into the macroporous SiO2-P support. SEM, N2 adsorption-desorption isotherms, TGA, XRD, FT-IR, (29)Si solid-state NMR and XPS spectroscopy were utilized to systematically characterize the physicochemical properties of the adsorbent...
April 19, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28514507/hydrogen-bond-involving-cavity-nh-protons-drives-supramolecular-oligomerization-of-amido-corroles
#18
Daniel T Gryko, Rafał Orłowski, Mariusz Tasior, Barbara Ventura, Olga Staszewska-Krajewska, Wojciech Schilf, Michał Cyrański, Łukasz Dobrzycki
Trans-A2B-Corroles with amide substituents at different positions versus the macrocyclic core have been synthesized. Their self-organizing properties have been comprehensively evaluated both in solid-state and in solution. The rigid arrangement of the amide functionality with the corrole ring led to the formation of strong intramolecular interactions and precluded intermolecular interactions. Replacement of sterically hindered C6F5 substituents at positions 5 and 15 with smaller electron-withdrawing CO2Me groups resulted in significant changes in the self-assembly pattern...
May 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28513727/self-assembled-air-stable-magnesium-hydride-embedded-in-3-d-activated-carbon-for-reversible-hydrogen-storage
#19
S S Shinde, Dong-Hyung Kim, Jin-Young Yu, Jung-Ho Lee
The rational design of stable, inexpensive catalysts with excellent hydrogen dynamics and sorption characteristics under realistic environments for reversible hydrogen storage remains a great challenge. Here, we present a simple and scalable strategy to fabricate a monodispersed, air-stable, magnesium hydride embedded in three-dimensional activated carbon with periodic synchronization of transition metals (MHCH). The high surface area, homogeneous distribution of MgH2 nanoparticles, excellent thermal stability, high energy density, steric confinement by carbon, and robust architecture of the catalyst resulted in a noticeable enhancement of the hydrogen storage performance...
May 17, 2017: Nanoscale
https://www.readbyqxmd.com/read/28509541/synthesis-characterization-and-variable-temperature-nmr-studies-of-silver-i-complexes-for-selective-nitrene-transfer
#20
Minxue Huang, Joshua R Corbin, Nicholas S Dolan, Charles G Fry, Anastasiya I Vinokur, Ilia A Guzei, Jennifer M Schomaker
An array of silver complexes supported by nitrogen-donor ligands catalyze the transformation of C═C and C-H bonds to valuable C-N bonds via nitrene transfer. The ability to achieve high chemoselectivity and site selectivity in an amination event requires an understanding of both the solid- and solution-state behavior of these catalysts. X-ray structural characterizations were helpful in determining ligand features that promote the formation of monomeric versus dimeric complexes. Variable-temperature (1)H and DOSY NMR experiments were especially useful for understanding how the ligand identity influences the nuclearity, coordination number, and fluxional behavior of silver(I) complexes in solution...
May 16, 2017: Inorganic Chemistry
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