Densification of sodium and magnesium aluminosilicate glasses at ambient temperature: structural investigations by solid-state nuclear magnetic resonance and molecular dynamics simulations.

Sodium and magnesium aluminosilicate glasses with compositions 20NaO-20AlO-60SiO (NAS) and 20MgO-20AlO-60SiO (MAS) were subjected to a 12 and 25 GPa compression and decompression at room temperature, resulting in density increases from 3.7% to 5.3% (NAS) and from 8.

Structural Aspects of Ambient-Temperature Densification of Highly Crack-Resistant Borosilicate and Aluminoborosilicate Glasses: Two Case Studies Examined by Solid-State NMR.

The structural aspects of ambient-temperature densification via pressurization at 25 GPa were studied by solid-state NMR for two case studies: An alkaline earth boroaluminosilicate glass with the composition 6CaO-3SrO-1BaO-10AlO-10BO-70SiO (labeled SAB) and a sodium magnesium borosilicate glass with the composition 10NaO-10MgO-20BO-60SiO (labeled MNBS). For SAB glass, cold pressurization results in significant increases in the average coordination numbers of both boron and aluminum, in line with previous results found in hot-compressed alkali aluminoborosilicate glasses. In addition, Al/B dipolar recoupling experiments reveal a significant decrease in the B/Al dipolar interaction strength upon pressurization, suggesting that the higher-coordinated boron and aluminum species experience weaker magnetic interactions.

Triclinic LaZnP with P, P, and P units: a combined study by P solid-state NMR spectroscopy and single crystal X-ray diffraction.

The ternary polyphosphide LaZnP was synthesized from the elements by using a salt flux or a ceramic method in sealed quartz ampoules. The obtained samples were investigated by X-ray powder and single crystal diffraction: own type, 1̄, = 775.33(13), = 827.

Polar covalent apex-base bonding in borapyramidanes probed by solid-state NMR and DFT calculations.

Pyramidane molecules have attracted chemists for many decades due to their regular shape, high symmetry and their correspondence in the macroscopic world. Recently, experimental access to a number of examples has been reported, in particular the rarely reported square pyramidal bora[4]pyramidanes. To describe the bonding situation of the nonclassical structure of pyramidanes, we present solid-state Nuclear Magnetic Resonance (NMR) as a versatile tool for deciphering such bonding properties for three now accessible bora[4]pyramidane and dibora[5]pyramidane molecules.

Extending the Palette of Luminescent Primary Thermometers: Yb/Pr Co-Doped Fluoride Phosphate Glasses.

The unique tunable properties of glasses make them versatile materials for developing numerous state-of-the-art optical technologies. To design new optical glasses with tailored properties, an extensive understanding of the intricate correlation between their chemical composition and physical properties is mandatory. By harnessing this knowledge, the full potential of vitreous matrices can be unlocked, driving advancements in the field of optical sensors.

Densification of Sodium Borosilicate Glasses at Ambient Temperature: Structural Investigations by Solid-State Nuclear Magnetic Resonance and Raman Scattering.

Alkali-borosilicate glasses with composition (80-)SiO-BO-20NaO (10 ≤ ≤ 30) were subjected to a 25 GPa compression and decompression at room temperature, resulting in density increases between 1.4% and 1.9%.

Structure of amorphous materials in the NASICON system Na1+xTiSiP3-xO.

The structure of glasses in the sodium (Na) super-ionic conductor (NASICON) system Na1+xTiSiP3-xOwith= 0.8 and= 1.0 was explored by combining neutron and high-energy x-ray diffraction withSi,P andNa solid-state nuclear magnetic resonance (NMR) spectroscopy.

Structural characterization of a new fluorophosphotellurite glass system.

While phosphotellurite glasses have superior properties over SiO-based glasses for many applications in optoelectronics and photonic devices, their high hydroxyl content limits their use in the mid-infrared range. This drawback can be overcome by fluoride addition to the formulation. In this work, we report the preparation, optical, and structural characterization of new glasses in the ternary system TeO-NaF-NaPO having the compositions 0.

Structure of diopside, enstatite, and magnesium aluminosilicate glasses: A joint approach using neutron and x-ray diffraction and solid-state NMR.

Neutron diffraction with magnesium isotope substitution, high energy x-ray diffraction, and Si, Al, and Mg solid-state nuclear magnetic resonance (NMR) spectroscopy were used to measure the structure of glassy diopside (CaMgSiO), enstatite (MgSiO), and four (MgO)(AlO)(SiO) glasses, with x = 0.375 or 0.25 along the 50 mol.

Oxy-Borylenes as Photoreductants: Synthesis and Application in Dehalogenation and Detosylation Reactions.

While the range of accessible borylenes has significantly broadened over the last decade, applications remain limited. Herein, we present tricoordinate oxy-borylenes as potent photoreductants that can be readily activated by visible light. Facile oxidation of CAAC stabilized oxy-borylenes (CAAC)(IPr Me )BOR (R=TMS, CH CH C H , CH CH (4-F)C H ) to their corresponding radical cations is achieved with mildly oxidizing ferrocenium ion.

Spectroscopic glimpses of the transition state of ATP hydrolysis trapped in a bacterial DnaB helicase.

The ATP hydrolysis transition state of motor proteins is a weakly populated protein state that can be stabilized and investigated by replacing ATP with chemical mimics. We present atomic-level structural and dynamic insights on a state created by ADP aluminum fluoride binding to the bacterial DnaB helicase from Helicobacter pylori. We determined the positioning of the metal ion cofactor within the active site using electron paramagnetic resonance, and identified the protein protons coordinating to the phosphate groups of ADP and DNA using proton-detected P,H solid-state nuclear magnetic resonance spectroscopy at fast magic-angle spinning > 100 kHz, as well as temperature-dependent proton chemical-shift values to prove their engagements in hydrogen bonds.

Structure of crystalline and amorphous materials in the NASICON system NaAlGe(PO).

The structure of crystalline and amorphous materials in the sodium (Na) super-ionic conductor system NaAlGe(PO) with x = 0, 0.4, and 0.8 was investigated by combining (i) neutron and x-ray powder diffraction and pair-distribution function analysis with (ii) Al and P magic angle spinning (MAS) and P/Na double-resonance nuclear magnetic resonance (NMR) spectroscopy.

The Bis(η -benzene)lithium Cation: A Fundamental Main-Group Organometallic Species.

The synthesis and characterization of the bis(η -benzene)lithium cation, the benzene metallocene of the lightest metal, is reported. The boron compound FmesBCl [Fmes: 2,4,6-tris(trifluoromethyl)phenyl] reacted with three molar equivalents of the lithio-acetylene reagent Li-C≡C-Fmxyl [Fmxyl: 3,5-bis(trifluoromethyl)phenyl]. Subsequent crystallization from benzene gave the [bis(η -benzene)Li] cation with the [{FmesB(-C≡C-Fmxyl) } Li] anion.

Solid-State Nuclear Magnetic Resonance Techniques for the Structural Characterization of Geminal Alane-Phosphane Frustrated Lewis Pairs and Secondary Adducts.

The first comprehensive solid-state nuclear magnetic resonance (NMR) characterization of geminal alane-phosphane frustrated Lewis pairs (Al/P FLPs) is reported. Their relevant NMR parameters (isotropic chemical shifts, direct and indirect Al- P spin-spin coupling constants, and Al nuclear electric quadrupole coupling tensor components) have been determined by numerical analysis of the experimental NMR line shapes and compared with values computed from the known crystal structures by using density functional theory (DFT) methods. Our work demonstrates that the P NMR chemical shifts for the studied Al/P FLPs are very sensitive to slight structural inequivalences.

Composition-Structure-Solubility Relationships in Borosilicate Glasses: Toward a Rational Design of Bioactive Glasses with Controlled Dissolution Behavior.

Owing to their fast but tunable degradation kinetics (in comparison to silicates) and excellent bioactivity, the past decade has witnessed an upsurge in the research interest of borate/borosilicate-based bioactive glasses for their potential use in a wide range of soft tissue regeneration applications. Nevertheless, most of these glasses have been developed using trial-and-error approaches wherein SiO has been gradually replaced by BO. One major reason for using this empirical approach is the complexity of short-to-intermediate range structures of these glasses which greatly complicate the development of a thorough understanding of composition-structure-solubility relationships in these systems.

Electronic effects in profluorescent benzotriazinyl radicals: a combined experimental and theoretical study.

The synthesis, photophysical characterization, and quantum chemical calculations of a series of benzotriazinyl radicals and their styryl radical trapping products are presented. The benzotriazinyl radicals are non-luminescent but surprisingly the corresponding styryl radical trapping products exhibit high fluorescence quantum yields (up to 60% in some cases), making them highly valuable probes or labels. Additionally, the influence of the substitution pattern on the optical properties of the radical trapping products was observed experimentally and interpreted by means of quantum chemical calculations.

Solid-State NMR Techniques for the Structural Characterization of Cyclic Aggregates Based on Borane-Phosphane Frustrated Lewis Pairs.

Modern solid-state NMR techniques offer a wide range of opportunities for the structural characterization of frustrated Lewis pairs (FLPs), their aggregates, and the products of cooperative addition reactions at their two Lewis centers. This information is extremely valuable for materials that elude structural characterization by X-ray diffraction because of their nanocrystalline or amorphous character, (pseudo-)polymorphism, or other types of disordering phenomena inherent in the solid state. Aside from simple chemical shift measurements using single-pulse or cross-polarization/magic-angle spinning NMR detection techniques, the availability of advanced multidimensional and double-resonance NMR methods greatly deepened the informational content of these experiments.

Effect of boron incorporation on the bioactivity, structure, and mechanical properties of ordered mesoporous bioactive glasses.

B2O3 doped (0.5-15 mol%) ordered mesoporous bioactive glasses (MBG) with the composition 80% SiO2-15% CaO-5% P2O5 were synthesized via a sol-gel based evaporation-induced self-assembly process using the block-copolymer P123 as a structure directing agent and characterized by biokinetic, mechanical and structural investigations. Nitrogen physisorption isotherms and electron microscopy indicate no detrimental effect of B2O3 on the ordered hexagonal pore structure.

Cycloaddition Reactions of an Active Cyclic Phosphane/Borane Pair with Alkenes, Alkynes, and Carbon Dioxide.

The active six-membered cyclo-FLP 6 undergoes a rapid P/B addition reaction to carbon dioxide. At elevated temperature, the resulting heterobicyclo[2.2.

From 3D to 2D: Structural, Spectroscopic and Theoretical Investigations of the Dimensionality Reduction in the [PtAl ] Polyanions of the Isotypic MPtAl Series (M=Ca-Ba, Eu).

Four new MPtAl (M=Ca, Sr, Ba, Eu) compounds, adopting the orthorhombic MgCuAl -type structure, have been synthesized from the elements using tantalum ampoules. All compounds are obtained as platelet-shaped crystallites and exhibit an increasing moisture sensitivity with increasing size of the formal M cation. Structural investigations indicate a pronounced elongation of the crystallographic b-axis, which results in a significant distortion of the [PtAl ] polyanion.

Dihydrogen Splitting by Intramolecular Borane-Phosphane Frustrated Lewis Pairs: A Comprehensive Characterization Strategy Using Solid State NMR and DFT Calculations.

Four hydrogenated intramolecular phosphane-borane frustrated Lewis pair (B/P FLP) compounds bearing unsaturated cyclic or aromatic carbon backbones have been synthesized and structurally characterized using B, P, H and H solid-state NMR spectroscopy. A comparison of the spectra with those of the corresponding free B/P FLPs shows that both B isotropic chemical shifts as well as nuclear electric quadrupolar coupling constants decrease significantly upon FLP hydrogenation, revealing the breakage of the partial B-P bond present in the starting materials. Likewise, the P isotropic chemical shift, the chemical shift anisotropy, and the asymmetry parameter decrease significantly upon FLP hydrogenation, reflecting the formation of a more symmetric, C -like local environment.

Rare-earth solid-state NMR spectroscopy of intermetallic compounds: The case of the Lu isotope.

The feasibility of high-resolution Lu solid-state NMR spectroscopy in intermetallic compounds crystallizing with cubic crystal structures is explored by magic-angle spinning NMR at different magnetic flux densities. The large quadrupole moment of this isotope (3.49 × 10 m) restricts observation of the NMR signal to nearly perfectly ordered crystalline samples.

Correlations of Crystal and Electronic Structure via NMR and X-ray Photoelectron Spectroscopies in the RETMAl (RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu; TM = Ni, Pd, Pt) Series.

A total of 35 intermetallic aluminum compounds have been synthesized from the elements via arc melting and characterized by powder X-ray diffraction. A total of 15 of them have been previously reported; however, detailed property investigations were missing. Compounds of the RETMAl (rare earth metal RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu) series with transition metal TM = Ni, Pd, and Pt crystallize isostructurally in the orthorhombic MgCuAl type structure ( Cmcm, oC16, fc).

Red-emitting KHFWOF:Mn for application in warm-white phosphor-converted LEDs - optical properties and magnetic resonance characterization.

We report novel efficient Mn4+ phosphors of composition K3HF2MO2F4:Mn4+ (M = Mo, W) containing [HF2]- and octahedral [MO2F4]2- building units. The phosphor exhibits strong absorption at 450 nm and an external quantum yield of 90%. K3HF2WO2F4:0.

Photophysical Properties of Ir(III) Complexes Immobilized in MCM-41 via Templated Synthesis.

In the search for understanding and improving the luminescence of optical materials based on Ir(III) complexes, three [Ir(CN)(dnbp)] (dnbp = 4,4'-dinonyl-2,2'-bipyridine) emitters were immobilized in MCM-41 mesoporous nanoparticles. By taking advantage of the amphiphilic nature of [Ir(CN)(dnbp)], the complexes were mixed with an appropriate surfactant and the resulting micelles served as templates for the synthesis of mesoporous silica host materials in a one-step sol-gel route. The MCM-encapsulated [Ir(CN)(dnbp)] complexes present intense emissions with prominent rigidochromic spectral changes that are substantially less affected by O as compared to methanolic solutions, with a thousand-fold decrease in quenching rate constants.